How many letters does the top answer for “an intersection or crossing of two tracts in the form of the letter x” have?

The most common answer is chiasm (6 letters).

Crossword clue: an intersection or crossing of two tracts in the form of the letter x

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

chiasm 6 letters wn-def

an intersection or crossing of two tracts in the form of the letter X

chiasma 7 letters wn-def

an intersection or crossing of two tracts in the form of the letter X

decussation 11 letters wn-def

an intersection or crossing of two tracts in the form of the letter X