To glean means to gather information or material bit by bit, often requiring patience and careful attention. When you glean facts from a book, you're picking out useful details from everything you read, the way you might collect seashells on a beach, choosing the best ones while leaving others behind.

The word comes from farming, where gleaning meant walking through harvested fields to collect the grain that machines or workers had missed. Poor families would glean these leftover stalks, gathering enough to make bread. It was slow, careful work that required bending down again and again to pick up individual pieces.

Today we use glean mostly for gathering knowledge. A detective might glean clues from a crime scene, noticing small details others overlook. You might glean your grandmother's opinions about politics from comments she makes during dinner, even though she never sits down and formally explains her views. Scientists glean data from experiments, historians glean facts from old documents, and you might glean what your teacher expects on an assignment by paying attention to everything she says in class.

The word suggests effort and attention: you can't glean by being lazy or careless. You have to actively look, think, and piece together what you find.