start right now/act without delay/Let's get cracking./No sooner said than done.

to speak / to say / to explain / to scold / to tell off / a theory (typically the last character in a compound, as in 日心說|日心说 heliocentric theory)

at once / right away / only / just (emphasis) / as early as / already / as soon as / then / in that case / as many as / even if / to approach / to move towards / to undertake / to engage in / to suffer / subjected to / to accomplish / to take advantage of / to go with (of foods) / with regard to / concerning