在大学课堂中，老师讲课常用的词汇和表达方式包括：

开始上课

Let's start class. It's time for class.

问候学生

Hello, boys and girls / children. Good morning / afternoon, boys and girls / teacher / students, morning good / afternoon good.

课堂管理

Stand up / Sit down, please. Is everyone / everybody here / present？

Is anyone/anybody absent？

Who’s absent？

与教师交流

I wonder if the prof took attendance already. （询问教授是否已经点名。）

其他基础词汇

a/an

abandon

abbreviation

abduct

abide

ability

able

abnormal

aboard

abolish

abort

abortion

abound

a bout

above

abreast

abroad

这些词汇和表达方式涵盖了大学课堂中常见的各种情景和需求，有助于教师和学生进行有效的沟通和教学活动。