Bulk refers to the large size, mass, or main portion of something. When you buy cereal in bulk at the store, you're buying a large quantity all at once, usually because it costs less per ounce that way. The bulk of an elephant is its massive body taking up space.

The word often describes the largest or most important part of something. If you spend the bulk of your afternoon reading, that means reading took up most of your time, even if you did other things too. A teacher might say that the bulk of the class understood the math lesson, meaning most students got it, though a few might still need help.

Something bulky is large and awkward to handle, like a thick winter coat that's hard to stuff into your backpack. You might also hear someone say they're trying to bulk up by lifting weights and eating more protein to build muscle mass.

When ships carry cargo, they often transport materials like grain, coal, or oil in bulk, meaning large amounts loaded loosely rather than in individual packages. This bulk cargo makes up a major share of goods shipped across oceans.