This is the 493rd most frequent Chinese word.
发
"发" means "to send," "to emit," "to develop," or "to grow," depending on context.
In this sentence, '发' is part of the verb '发送', meaning 'to send'.
我每天都发送邮件给客户。
I send emails to clients every day.
In this case, '发' is used in '发烧', meaning 'to have a fever'.
她感冒发烧了，需要休息。
She has a fever due to a cold and needs rest.
Here, '发' is used in '发出', meaning 'to emit or give off', often related to emotions or physical expressions.