incidentally

Imagine you're telling a story, and then you add, "Incidentally, I saw your brother at the station." Here, the word tells your listener that this is extra information, not the main point. Very often, it works a lot like "by the way" or "as a side note." It can also mean that something happened by chance. If you say, "I incidentally ran into my old teacher there," you mean the meeting was not planned. So this word often points either to a small side remark or to something that happened accidentally while something else was going on.

"Incidentally" is an adverb with two common uses. First, it can introduce a side remark, much like saying "by the way." In this use, you bring in a detail that is connected to the topic but is not the main point. For example: "The restaurant was very crowded. Incidentally, they also had live music." The music is not the central idea, but it is a useful or interesting extra detail.

Second, "incidentally" can mean "by chance" or "not intentionally." In this sense, it describes something that happened along the way rather than by plan. For example: "I incidentally met my old teacher at the zoo." This means the meeting happened accidentally, not because it was arranged.

These two meanings are related because both involve something that is not central or not planned. Sometimes the word points to an extra comment in conversation; sometimes it points to an unexpected event. The exact meaning usually becomes clear from the sentence around it.

In everyday English, the "by the way" meaning is especially common. The "by chance" meaning is also correct, though it often appears in more formal writing. In both cases, the word helps the speaker move lightly away from the main point for a moment, either to add a side note or to mention something that happened unexpectedly.