Fellow is a versatile English word with multiple meanings:
1. A man or boy (informal): "He's a nice fellow."
2. A member of a learned society: "She was elected a Fellow of the Royal Society."
3. A graduate student receiving financial support: "He's a research fellow at Harvard."
4. A companion or associate: "We were fellow travelers on the journey."
5. An equal or peer: "She treated me as her fellow."
6. (Adjective) Belonging to the same group: "fellow citizens"