infrequent (adj.) infrequency (n.) infrastructure (n.) infrasonic (adj.) infralapsarian (adj.) infraction (n.) infra-red (adj.) infra- 表示“在下, 在下文”之义infra dig. infra (adv.) infotainment (n.) infortunate (adj.) informs v.通知；告诉；使熟悉；告发；赋特征于informer (n.) informed (adj.) informative (adj.) informational (adj.) information (n.) information n.信息；情报；资料；通知informatics (n.)