expression, godan verb (-ku)
gain strength; increase ability; become stronger
Used for physical strength, skill, or ability that improves through effort or experience. Often implies a gradual process.
See also: 付く (つく)
毎日練習すれば、必ず力が付く。
If you practice every day, you will definitely gain strength.
この問題集をやれば、英語の力が付く。
If you work through this workbook, your English ability will improve.