Words that work together often grow together. They have an arc: they start out as separate words, they move to having a hyphen between them, and they end as a single word.
Think of the cloth cap baseball players wear.
It started out as a baseball cap.
Then it became a ball cap.
Then it became a ball-cap.
Now it’s a ballcap.
Writers aren’t always consistent: we found a web site that sold ballcaps and ball caps.
Some words skip the hyphenated stage. Think of the computer program that manages your information:
It started out as a data base.
Then it became—and now is—a database.
Again: Use a good dictionary (usually one not more than ten years old). If the listing offers more than one possibility, use the first one. That one’s the most accepted.
If you have questions, let us know. We love this stuff.
Next week: We’ll pursue Jackie Mattila’s questions about i.e. and e.g. What do they mean? When should we use them?