These five verbs all describe making something easier or more successful, but they emphasize different kinds of action. They often overlap: the best choice depends on the situation, not a strict rule.
- Help is the broadest, most natural everyday choice. It can describe practical action or anything that makes a situation better. Could you help me carry this box?
- Assist usually sounds more formal. It often describes taking part in a task or providing a service. A staff member assisted us with the booking. In casual conversation, a simpler word may sound friendlier.
- Aid is also fairly formal. It often describes improving recovery, learning, or another process, or providing help in serious situations. Regular practice aids language learning. It is not limited to emergencies.
- Support often emphasizes giving someone the resources, encouragement, or practical backing they need, sometimes over time. Her family supported her during her training. This does not necessarily mean doing her tasks for her.
- Facilitate means making a process or activity easier or smoother, often by arranging suitable conditions. The teacher facilitated the discussion by giving everyone a turn. The teacher enabled participation rather than supplying every answer.
Notice the grammar, too: you can help someone do something, assist someone with something, or facilitate something. Avoid treating every verb as a direct replacement in the same sentence pattern.