An expression meaning “in addition to ...” used to add extra information or elements (as in “in addition to X, Y”).
彼は英語に加えて中国語も話せる。
In addition to English, he can also speak Chinese.
給料に加えて手当が支給される。
Allowances are provided in addition to the salary.
今年は猛暑に加えて大雨も多かった。
This year there was heavy rain in addition to the intense heat.