by the

by the (unit)

For each unit, as of items sold in this manner. How much does this meat cost by the pound? My sewing machine isn't working at the moment, so I certainly don't need fabric by the yard right now! You can't just get one cupcake at that place—they only sell them by the dozen, like eggs.

by the by

Incidentally; on a side note; by the way. An interjection meant to casually introduce or emphasize additional information in the conversation. Sometimes, though less commonly, written as "by the bye." By the by, I remembered where I left my keys, in case you were wondering. Beckett was an amazing playwright. There's a lecture on his work tomorrow, by the by. By the by, I'll be home late tonight. The printer jammed, so that set us back with finalizing our report.

by the

bye/by

By the way; incidentally.