# Membership and federation affiliation of physics societies
Physics societies organize the profession in different ways. Individual-membership societies such as the [American Physical Society](https://www.edgepedia.org/american-physical-society) (APS) have people as their members;[1](https://www.aps.org/about/news/2026/06/membership-plan-options-expand) territorial federations such as the [International Union of Pure and Applied Physics](https://www.edgepedia.org/international-union-of-pure-and-applied-physics) (IUPAP) have as members communities of physicists in a defined territory;[2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/) and regional societies such as the [European Physical Society](https://www.edgepedia.org/european-physical-society) (EPS) and the Association of Asia Pacific Physics Societies (AAPPS) maintain observer relationships with IUPAP.[3](https://iupap.org/who-we-are/liaison-with-other-organizations/) This article compares how these bodies count members, how IUPAP membership and dues work, and what the figures do and do not tell you.
| Fact | Figure | Source |
|---|---|---|
| IUPAP territorial members | 52 (2024–2025) | [4](https://iupap.org/who-we-are/members/) |
| IUPAP members in arrears over 3 years | 8; none excluded for 2025 | [5](https://indico.global/event/15318/contributions/131516/attachments/63874/123390/IUPAP%20Membership%20and%20Development%20v02.pdf) |
| IUPAP General Assembly meets | Every 3 years | [2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/) |
| APS membership | More than 50,000 scientists | [1](https://www.aps.org/about/news/2026/06/membership-plan-options-expand) |
| IUPAP observers (non-voting) | APS, EPS, AAPPS, AfPS, UK IoP, FEIASOFI | [3](https://iupap.org/who-we-are/liaison-with-other-organizations/) |
| IAPS (student body) | 39 Territorial Committees, 15 Local Committees, ~150 Individual Members | [6](https://iaps.info/members/) |
| APS discount for lower-income countries | Up to 90% | [1](https://www.aps.org/about/news/2026/06/membership-plan-options-expand) |
## What counts as a physics society membership
Membership means different things in different bodies, so headline figures are not directly comparable.
**Individual members** are people who join a society and pay dues. APS describes itself as a membership organization of more than 50,000 scientists.[1](https://www.aps.org/about/news/2026/06/membership-plan-options-expand) At the student level, the [International Association of Physics Students](https://www.edgepedia.org/international-association-of-physics-students) counts 39 Territorial Committees, 15 Local Committees, and around 150 Individual Members; students without access to a national or local committee can join individually.[6](https://iaps.info/members/)
**Territorial members** are not people at all. IUPAP's members are communities of physicists engaged in independent scientific activity within a definite territory, and the statutes state that the word "territory" does not imply any political position on the part of the Union.[2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/) A territory adheres through an appropriate body, such as its principal scientific academy, national research council, or an association representing its broad physics community, or failing these its government.[2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/) For example, the US adhering body is the National Academy of Sciences in Washington, DC.[4](https://iupap.org/who-we-are/members/) Many territorial members adhere through a body that is not the country's physical society.[3](https://iupap.org/who-we-are/liaison-with-other-organizations/) This is the key distinction between individual-membership societies and academy-affiliated representation: joining APS is an individual choice, while IUPAP seats are held by national institutions.
**Corporate associates** are companies rather than physicists; CAEN was accepted as a Corporate Associate Member holding 1 unit under an MOU signed on 22 February 2024.[7](https://indico.global/event/7208/contributions/67076/attachments/32383/60082/Resolutions_Membership.pdf)
## How IUPAP membership works
Each adhering body sets up a Liaison Committee to maintain relations between its physics community and the Union.[2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/) In Japan, the liaison is the Science Council of Japan; the Physical Society of Japan notes that national physics societies and science academies serve as these points of contact.[8](https://www.jps.or.jp/english/about-jps/iupap/about-iupap.html)
**Dues and votes are share-based.** A member's dues equal its number of shares multiplied by the per-share dues set by the General Assembly. Voting rights scale with shares: one share gives one vote, and sixteen or more shares give six votes; members paying less than one share have no vote.[2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/) The General Assembly, which meets every three years, is the highest governing body: it accepts new members, sets dues, and elects the Executive Council and Commission members.[2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/)
**Arrears rules are strict.** A member in arrears for three years loses its right to vote in the General Assembly; a member in arrears for six years is excluded from the Union.[2](https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/)
**Membership categories** include full territorial members, Associate Territorial Members, and Personal Members. Associate Territorial Membership exists to facilitate a first step towards full membership: small national physics communities from developing territories must commit to grow their physics activities, and IUPAP monitors progress over a renewable three-year period.[4](https://iupap.org/who-we-are/members/) Personal Members are ex-officio, comprising only the Chairs of IUPAP Commissions or Affiliated Commissions; they have voting rights but are exempted from dues.[4](https://iupap.org/who-we-are/members/)
## Regional federations and observers
IUPAP maintains observer relationships with regional and national societies: the American Physical Society (APS), European Physical Society (EPS), Association of Asia Pacific Physics Societies (AAPPS), African Physical Society (AfPS), UK Institute of Physics (IoP), and the Ibero-American Association of Physical Societies (FEIASOFI). Observers may be invited to send a representative to Council meetings and General Assemblies but have no voting privileges.[3](https://iupap.org/who-we-are/liaison-with-other-organizations/) A large individual society such as APS therefore sits outside IUPAP's voting structure, while the US physics community participates through the National Academy of Sciences.[4](https://iupap.org/who-we-are/members/)
The [American Institute of Physics](https://www.edgepedia.org/american-institute-of-physics) (AIP) uses a different federation model altogether: each Member Society appoints a Director to the AIP Board and two delegates to the AIP Federation Assembly, an institutional society-based structure rather than a territorial one.[9](https://www.aip.org/federation)
## By the numbers: recent membership
The official roster currently lists 52 territorial members.[4](https://iupap.org/who-we-are/members/) The Physical Society of Japan reported 60 member countries as of 2022,[8](https://www.jps.or.jp/english/about-jps/iupap/about-iupap.html) a discrepancy with the official roster's 52 that reflects differences in date and counting method; the current official figure of 52 is the one to use.[4](https://iupap.org/who-we-are/members/)
Recent changes documented in the 33rd General Assembly resolutions:
- **South Africa** was upgraded from Category 3 to Category 5, approved by Council on 11 October 2023 and ratified at the Assembly, giving it 3 votes with effect in 2024.[7](https://indico.global/event/7208/contributions/67076/attachments/32383/60082/Resolutions_Membership.pdf)
- **Nigeria** was reinstated as a Category 1 Territorial Member on 23 November 2023, with the Nigerian Institute of Physics as adhering body under an MOU.[7](https://indico.global/event/7208/contributions/67076/attachments/32383/60082/Resolutions_Membership.pdf)
- **Jordan** resumed membership as a Category 1 Territorial Member on 22 March 2024, with the Jordan Atomic Energy Commission as its Liaison Committee under an MOU signed with IUPAP President Michel Spiro.[7](https://indico.global/event/7208/contributions/67076/attachments/32383/60082/Resolutions_Membership.pdf)
- **Nepal** became the first Associate Territorial Member and is deployed on Commission C13 (development) and Working Group 21 (climate).[5](https://indico.global/event/15318/contributions/131516/attachments/63874/123390/IUPAP%20Membership%20and%20Development%20v02.pdf)
As of 2025, no member has been excluded after six years of arrears, but 8 members are in arrears of more than 3 years and have accordingly lost their votes.[5](https://indico.global/event/15318/contributions/131516/attachments/63874/123390/IUPAP%20Membership%20and%20Development%20v02.pdf)
On the individual-society side, APS replaced its single-membership model in June 2026 with Basic and Full plans, introducing discounts of up to 90% for residents of lower-income and lower-middle-income countries as defined by the World Bank; members must demonstrate residency during the join process.[1](https://www.aps.org/about/news/2026/06/membership-plan-options-expand) Both plans include access to APS News and Physics magazine, unit membership options, access to APS Fellowship, and voting in the APS general election; the Full plan adds [Physics Today](https://www.edgepedia.org/physics-today) access, mentorship resources, and meeting discounts.[1](https://www.aps.org/about/news/2026/06/membership-plan-options-expand)
## References
1. American Physical Society expands membership plan options, https://www.aps.org/about/news/2026/06/membership-plan-options-expand
2. Statutes – IUPAP (archived), https://web.archive.org/web/20190326143613/http://iupap.org/about-us/statutes/
3. Liaison With Other Organizations – IUPAP, https://iupap.org/who-we-are/liaison-with-other-organizations/
4. Members – IUPAP, https://iupap.org/who-we-are/members/
5. IUPAP Membership and Development (2025 presentation), https://indico.global/event/15318/contributions/131516/attachments/63874/123390/IUPAP%20Membership%20and%20Development%20v02.pdf
6. Members – IAPS, https://iaps.info/members/
7. IUPAP 33rd General Assembly Resolutions: Membership and Units, https://indico.global/event/7208/contributions/67076/attachments/32383/60082/Resolutions_Membership.pdf
8. About IUPAP – The Physical Society of Japan, https://www.jps.or.jp/english/about-jps/iupap/about-iupap.html
9. AIP Federation – AIP.ORG, https://www.aip.org/federation
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*Topic: Encyclopedia › Physical world and mathematics › Physics › Physics methods, practice, and community › Physics publications, awards, and institutions › Physics society and institution records › Society membership and affiliation records*
*Initially written Sep 17, 2026 · Edited: Oct 11, 2026; Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license