How many letters does the top answer for “occurring or existing at the same time or having the same period or phase” have?

The most common answer is synchronal (10 letters).

Crossword clue: occurring or existing at the same time or having the same period or phase

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

synchronal 10 letters wn-def

occurring or existing at the same time or having the same period or phase

synchronous 11 letters wn-def

occurring or existing at the same time or having the same period or phase