fill gap

You can use it as a verb phrase. Usually, you say fill the gap or fill a gap. Sometimes you might say fill in the gap. It works for physical spaces, but it is much more common for abstract ideas. If you are hiring a new person, they fill the gap left by the old employee. If you eat a small snack because you are hungry before dinner, that snack fills the gap. It is a very flexible and handy tool for your vocabulary.

Use it when something is clearly missing. At work, use it when a project needs a specific skill you don't have yet. In school, use it when you finally understand a difficult topic. With friends, use it when someone stops talking and the silence feels awkward. It is perfect for problem-solving scenarios. If you find a clever way to fix a small problem, you are filling a gap in the system.

Do not use it for massive, emotional life changes. You wouldn't usually say a new spouse fills the gap of an ex-partner; that sounds a bit robotic! Also, avoid using it for overflowing things. If a cup is already full, you aren't filling a gap. It is only for when something is noticeably empty or lacking. Don't use it for 'filling a glass' with water—that is just filling a glass.

In English-speaking cultures, efficiency is highly valued. We don't like 'gaps' in logic, employment, or service. The phrase became very popular in business and recruitment. We often talk about a gap year (a year off between school and university). If you do something productive during that time, you are filling the gap in your resume. It reflects a culture that likes to stay busy and complete tasks.

You will often hear bridge the gap. This is slightly different. Bridging means connecting two separate things. Filling means putting something inside the hole. You might also hear fill the void, which is much more dramatic and emotional. Use fill the gap for everyday logic and fill the void for deep, poetic longing after a breakup or a loss.