The Check ▾ dropdown and the Word Information popup help you understand and choose words.

Check dropdown listing Look up, Thesaurus / synonyms, Show homophones and Clear homophones.
The Check dropdown. Show and Clear homophones are available when Word or Pages is in front.
Look Up and Thesaurus
Look a word up in the macOS Dictionary, or see synonyms for it.
Word popup (Control+Shift)
Hold Control and Shift over a word to see its symbol, syllables, definition, synonyms and homophones.
Homophones
Colour every homophone in a Word or Pages document blue, so you can check you’ve used the right one.