bonus
Synonym discussion
Sense: noun/1
For noun/1, a bonus is extra money added to what someone normally gets. A reward is wider: it can be money, but it can also be praise, a gift, or a prize. An incentive usually looks forward, because it is meant to push people to work harder or sell more. Commission is a regular payment based on sales, often a fixed percentage, so it feels more built into the job than a bonus. Perk is different again: it usually means a pleasant extra benefit, such as free meals, rather than direct cash. You might say, 'The staff received a year-end bonus,' but 'Sales staff earn commission on each car,' and 'Free gym access is a perk.'
Etymology
English borrowed bonus from Latin, where bonus meant 'good'. The noun developed the idea of something extra added because it is favorable or welcome, and it later became especially common for extra payment in work and business.