Worked example: big
LARGE is a neutral close synonym for BIG. HUGE adds greater intensity, while MAJOR often describes importance rather than physical size. SMALL is a common opposite for size, but MINOR is the clearer contrast when the intended sense is importance.
- same topic?
- same strength?
- same grammar?
- same tone?
Make a meaning scale
Place three related words from weaker to stronger, then write one sentence where each is the best fit. Repeat with an opposite pair in the same sense. This makes intensity and context visible instead of treating a thesaurus result as an automatic replacement.
Similarity is not interchangeability
A synonym can change tone, intensity, grammar, or the sense of a sentence. Read the usage note beside each relationship and test the candidate in context. The tool compares reviewed senses rather than claiming that one word can replace another everywhere.