How many letters does the top answer for “another word for third” have?

The most common answer is tertiary (8 letters).

Crossword clue: another word for third

3 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

tertiary 8 letters gen-syn

from 63 million to 2 million years ago

thirdly 7 letters gen-syn

in the third place

tierce 6 letters gen-syn

one of three equal parts of a divisible whole

another word for about 50% similar → approximately, roughly, some

another word for terms 50% similar → footing

another word for under 50% similar → nether

another word for word 50% similar → phrase