A grammar textbook entry. 接尾辞 ('suffix') is a technical linguistic term — 接尾 (attached-to-end) + 辞 (word, particle). 意を表す (いをあらわす) uses the classical/literary short form 意 (the full form is 意味) — 'express a meaning.' Common in classical-influenced or technical writing. ~などの意を表す名詞 = 'nouns that express meanings such as X, Y, Z, etc.' The whole sentence is formatted as a dictionary/textbook entry with a numbered point and a list of categories inside quotes. The plain form (non-polite) is typical of reference materials.