We often speak of the need for 'timing' in comedy: "You have to know when to 'time' the punch line"..."He has good comic 'timing'...etc."...but we rarely speak of timing in drama?
Like good comedy timing, good dramatic timing is a function of the consummately disciplined absorption and release of emotion.
In comedy, the punch line--the joke--comes just at the end-point of maximally emotional tension--which is just prior to the point where the audience would choose to release the actor-induced tension on their own; in comedy tension, if tension is too early released by a joke, there results too little laughter; too late a release, the joke falls flat.
In drama, the actor similarly releases his/her inner tension not into a joke but into the next line, or movement, or facial reaction, or prop manipulation. The 'action' results at the excruciatingly (and final) tense moment, at the point when the actor-as-character, feeling the real emotional tension of the scene, unconsciously--as in real life--releases the most effective outwardly-released 'action' at the other character, in the utterance of the line, or other physical movement.
In both comedy and drama, therefore, timing is an inner, unconscious, spontaneous systemic 'action', an all-too-human perfect-moment-of-release of the inner tension felt by the character(s) in the scene.
Good 'timing', like good acting, is always real (all good acting is lived onstage as in life...only more excitingly). Therefore, good timing, dramatic or comedic, finds its most fertile ground in the onstage emotionally brave; in those actors-as-characters willing and able to feel, sustain, absorb and release their emotion at the last possible moment of tension, thereby heightening the performance effect.
Actor (as opposed to character) uncomfortableness-with-emotion, becomes the death knell for good dramatic (and comedic) 'timing'. Emotional experience--the constant practice and development of both intense performance absorption and 'timed' release of performance-induced emotion--is the actors' corallary antidote.