GRE TOEFL IELTS optional Definition Not required; left to personal choice. 日本語 必須ではない; 個人的な選択に任せる Example "Wearing a hat is optional during the tour." Sign in to save GRE Quiz → TOEFL Quiz → IELTS Quiz → ← option optometrist → Study tips featuring "optional" Map Each Word Into a Connected Network Audit Your Own Writing for Lexical Resource Force Contrast Between Two Similar Words Related words GRE awe GRE smithereens GRE abacus SAT abase GRE abash GRE abate GRE abbreviate GRE abbreviation SAT abdicate SAT abdomen GRE abduct GRE aberrant