我正在读一本心理学入门书，以打好扎实的基础。

I'm reading an ___introduction to psychology to get a solid foundation in the subject.

宣传册提到一个周末课程，作为飞行入门课。

The brochure mentions a weekend course that serves as an ___introduction to flying.

在深入学习更高级的主题之前，她上了一门在线的编程入门课。

She took an online ___introduction to programming before diving into more advanced topics.