solely engrossed in one thing; just (one thing, no need to worry about the rest); simply; by all means; please feel free; do not hesitate (to ask for sth)[cedict]
开
kāiㄎㄞ
to open; to start; to turn on; to write out (a medical prescription); to operate (vehicle); abbr. for 開爾文|开尔文 degrees Kelvin[cedict]