An indentation is a space or gap set back from the edge of something. When you start a new paragraph in an essay, you often leave a small indentation at the beginning of the first line, moving it slightly to the right of where other lines start. This helps readers see where a new thought begins.

The word can describe any inward cut or notch. A carpenter might notice an indentation in a piece of wood where something pressed against it. If you lean against a pillow, you'll leave an indentation where your head was. Coastlines often have indentations where the ocean cuts into the land, forming bays and coves.

In writing and programming, indentation serves an important purpose beyond decoration. When you indent lines of text or code, you create a visual structure that shows how ideas relate to each other. A bulleted list uses indentation to show which points are main ideas and which are supporting details. Programmers rely heavily on careful indentation to keep their code readable and organized.