Per is a preposition that is used to indicate a rate, ratio, or proportion of something. There are several synonyms for the word per, including "by the," "for each," "each," and "every." For example, if an item costs $10 per unit, it means that you will be paying $10 for each unit you purchase. Similarly, if you receive a salary of $50,000 per year, it means that you will be earning $50,000 every year. Other synonyms for per include "pro rata," "according to," "in proportion to," and "commensurate with." Overall, understanding the synonyms for per can help improve your communication skills and make your writing more effective.