Linguists use morphological and distributional evidence to determine word classes (not meaning!).
Morphological evidence includes the derivational [[morphology]] of words (e.g., *walked* is probably a verb because *walk* is a verb). Distributional evidence is derived from the words nearby neighbors (e.g., a word preceded by an adjective is probably a noun).
There is no standard list of parts of speech that works for all languages, but a universal set has been established that covers most needs from the Universal Dependencies project.
**Open Class words**: class of words where new words may occur
- ADJ (Adjective)
- ADV (Adverb)
- INTJ (Interjection)
- NOUN
- PROPN (Proper noun)
- VERB
**Closed class words**: class of words where new words will not occur
- ADP (Adposition)
- AUX (Auxilaary)
- CONJ (Conjunction)
- DET (Determiner)
- NUM
- PART
- PRON
**Other**
- PUNCT (Punctuation)
- SYM (Symbol)
- X