GRE TOEFL IELTS optional Definition Not required; left to personal choice. 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" Audit Your Own Writing to Find Gaps Write GRE Words Into Your Own Sentences TOEFL Academic Vocabulary: Study by Topic Related words GRE swill GRE taper GRE testy GRE abacus SAT abase GRE abash GRE abate GRE abbreviate GRE abbreviation SAT abdicate SAT abdomen GRE abduct