How should I refer to a person when I’m unsure of the gender? He? They? 
I’m not trying to start a gender politic thing here - just want to avoid coding errors.
Do you mean in the source code? I think you can use “it,” “he,” “she,” or “they.”
[code]Lab is a room.
Bob is a man in Lab. Jane is a woman in lab.
Definition: a person is other if it is not the player.
Definition: a person is very other if he is not the player.
Definition: a person is really other if she is not the player.
Definition: a person is truly other if they are not the player.
When play begins:
say “Jane is[if Jane is very other] very[end if][if Jane is truly other] truly[end if][if Jane is really other] really[end if][if Jane is other] other[end if].”;
say “Bob is[if Bob is very other] very[end if][if Bob is truly other] truly[end if][if Bob is really other] really[end if][if Bob is other] other[end if].”[/code]
All the definitions work as expected.
In your own prose… well, you can make your own mind up.
Thanks for testing! 
Yes, it looks like Inform doesn’t differentiates between he/she/they/it. A bit like that Inform doesn’t care if you say “a/an/the” before a thing (except in the line where you create said thing.)
Looks like you can refer to non-living things with he/she too:
Lab is a room.
A refrigerator is a device in Lab.
Definition: a device is spoon-like if she is switched on.But turning on the thing and typing showme refrigerator doesn’t display ‘spoon-like’?
Yeah, the SHOWME command in general doesn’t show adjectives that are defined by “Definition:”. I think it shows properties (like if you said “A device can be spoon-like”) because those are stored as part of the representation of the thing, but defined adjectives are calculated rather than directly stored.