GRE TOEFL IELTS optional Definition Not required; left to personal choice. 中文 非必需的;由个人选择决定的。 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" Study the Exact Words Examiners Use Group Words Together by Emotional Tone Map Each Word Into a Connected Network 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