This is the 4996th most frequent Russian word.
лекцию
"Лекцию" means "lecture" in English.
Here, 'лекцию' describes the object of the action performed during the lecture—an activity the students attended.
Студенты слушали увлекательную лекцию, приглашённого профессора.
The students listened to an engaging lecture by a guest professor.
In this sentence, 'лекции' is in the instrumental case, referring to the lecture's timing and association with subsequent activities.
После лекции профессор ответил на вопросы студентов.
After the lecture, the professor answered the students' questions.
The word 'лекцию' is the object of the verb 'прочитаю', indicating a lecture that the speaker will be delivering.