The colon: well-loved but, oh, so misunderstood. The colon is not just used to introduce a list; it is far more flexible. The colon can be used after the first word of a sentence or just before the final word of a sentence. The colon can also be used to introduce a grammatically independent sentence. Thus, it is one of the most powerful punctuation marks.

The colon is like a sign on the highway, announcing that something important is coming. It acts as an arrow pointing forward, telling you to read on for important information. A common analogy used to explain the colon is that it acts like a flare in the road, signaling that something meaningful lies ahead.

Use the colon when you wish to provide pithy emphasis.

To address this problem, we must turn to one of the biologist’s most fundamental tools: the Petri dish.

Use the colon to introduce material that explains, amplifies, or summaries what has preceded it.

The Petri dish: one of the biologist’s most fundamental tools.

In low carbon steels, banding tends to affect two properties in particular: tensile ductility and yield strength.

The colon is also commonly used to present a list or series, which comes in handy when there is a lot of similar material to join:

A compost facility may not be located as follows: within 300 feet of an exceptional-value wetland; within 100 feet of a perennial stream; within 50 feet of a property line.