lecture

Compared meaning: a formal talk to an audience (noun).

比较义项：演讲（名词）。

• speech

  General word for a formal talk to an audience on any occasion (ceremony, political rally, motivational event); not necessarily meant to teach a subject.

  泛指在任何场合（典礼、政治集会、励志活动等）对听众发表的正式讲话，不一定以传授某学科知识为目的。

  The mayor gave a moving speech at the city's anniversary celebration.

  市长在城市周年庆典上发表了一场感人的演讲。

• lecture 本词

  A talk given specifically to teach an audience about a subject, typically in an academic or educational setting, often as part of a course.

  专指以向听众传授某学科知识为目的的讲话，通常在学术或教育场合进行，常是课程的一部分。

  Every Monday, the professor gives a lecture on medieval European history to first-year students.

  每周一，教授都会给大一新生讲一节关于中世纪欧洲历史的课。

Speech and lecture both mean a formal talk to an audience. Lecture stresses teaching a subject, usually in a classroom. Speech is more general, used for any occasion, not necessarily to teach. Not compared: speech as 'ability to talk', or lecture meaning 'to scold'.

这两个词都指对听众发表的正式讲话，在“演讲”这个意义上容易混淆；但 lecture 强调以传授学科知识为目的，常见于课堂或学术场合，speech 则泛指各种场合（典礼、政治、励志演讲等）的正式讲话，不一定具有教学性质。这里不比较 speech 表示“说话能力”的义项，也不比较 lecture 作动词表示“训斥，说教”的用法。