tender has 22 distinct synonyms spread across 11 of its 18 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is tough.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
given to sympathy or gentleness or sentimentality
“a tender heart”
something that can be used as an official medium of payment
someone who waits on or tends to or attends to the needs of another
2 of the 18 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for tender.
Synonyms, antonyms and the broader and narrower relations for tender come from Princeton University’s WordNet. Full sources and licences.
a formal proposal to buy at a specified price
car attached to a locomotive to carry fuel and water
a boat for communication between ship and shore
make a tender of; in legal settlements