【形】〔人に〕役立つ, 助けになる〔to〕；〔…の点で〕有益な〔in〕‖〜 suggestions [hints, ideas] 役に立つ助言[ヒント, 考え]/This encyclopedia is always 〜 to me. この百科事典はいつも私の役に立ちます/It was very 〜 of you to mow the lawn. 君が芝生を刈ってくれてとても助かった《◆You were 〜 to mow ... ともいう. It was very 〜 that you mowed the lawn. は普通ではない》.