Why choose this word, when that one is almost the same?  Writing is concerned in a big way with nuance, the subtlest of distinctions, and the choice of one word or another can say a lot about the character who says it, if it’s used in dialogue, or precise details of the scene. 

Here’s the opening sentence of my pilot episode script for The Sharp End:

“Lean and muscled LEON CARR (30) gets out of his car and prowls across to a squalid house in a low-income neighbourhood.” 

What is it about Leon that means he prowls, rather than just walking over the road?  It’s connected to the fact that he’s lean and muscular: his physicality is a big defining factor, while many of the other characters in the same script are described by reference to their clothes than their body type; Dawn Catchpole, for instance, is “all neon and noir”, and Savita Dhatri is “dressed for a party”. 

The objective is to capture something of the essence of the character in as few words as possible.   Same with scene-setting.  Check out the differences between these essentially similar descriptions:

BARRY lies face down on the floor.  He’s in his 20s, dressed in leisurewear.  His mobile phone is beyond his outstretched hand, and rings with an Oasis tune.  His eyes flicker as he hears it, and he stretches for the phone, his movements pained.  Congealed blood circles his baseball cap.

He gets to his knees, and answers the phone.  He looks around as he does.

BARRY

Hello?  Dunno mate.  Looks like I’m in a warehouse.

And now, this take on the same action:

High ceiling, and blank walls.  A big still space, that suddenly echoes with a classic rock tune ringing incessantly from a mobile phone.  A man’s hand twitches on the floor, and reaches for the phone.  BARRY is in his 20s, dressed in tracksuit bottoms, a sweatshirt and trainers.  He looks like he’s been badly beaten up.  The phone continues to ring.  With an effort, he manages to reach it, and sits up as he does.

BARRY

Hello?

(Looking around.)

Don’t know, mate.  Haven’t got a clue.

The choice of words, and sequence of information, presents two very different ways of filming what amounts to the same scene.  The first has Barry as its focus, while in the second the camera takes in the warehouse interior before settling on its occupant.  Odds are, the second would be shot with a hand the first indication of Barry’s presence, while in the first he’s seen lying down from the beginning.  And so on: what other differences in how the two versions of the scene would be shot are implicit in the way they’re written?

Pretty much every book on screenwriting will tell you not to indicate camera moves and so on, since these are the remit of the director and not the writer.  But effective use of language within the script can help you to direct the director, by creating pictures in their head that they can then realise with the aid of cast and crew.