Sufficient means enough to meet a need or accomplish a purpose. When you have sufficient time to finish your homework before dinner, you have as much time as you need. When a recipe calls for sufficient flour to make the dough stick together, it means you need just enough flour to do the job, not too little and not necessarily extra.

The word focuses on meeting a specific requirement or standard. Three hours might be sufficient time to read a book, but insufficient time to read three books. A glass of water might be sufficient to quench your thirst, but insufficient to water a garden. What counts as sufficient depends entirely on what you're trying to accomplish.

You'll often hear sufficient paired with its opposite, insufficient. If a student gives insufficient evidence in an essay, they haven't provided enough proof to support their argument. If they give sufficient evidence, they've done enough to make their case convincing.

The related word suffice means “to be sufficient.” When your teacher says “one example will suffice,” she means one example is enough. People sometimes say “suffice it to say” before making a point, meaning “it's enough to say this much” without going into every detail.