Properties are key/value pairs which are assigned to a thing. The collection itself is also a thing to which properties can be assigned. For example: .answer = 42; creates a property answer with value 42 and the property will be assigned to the collection.

The key of a property must be of type string. If the key is not a valid name, then the property can be set by using the square bracket [..] notation or the set(..) / get(..) functions can be used.

There are 16, single character keys that are reserved for ThingsDB and cannot be used as key strings:

key description
(space) unused
! Reserved for errors.
" Reserved for timeval.
# Reserved for thing ID’s.
$ Reserved for sets.
% Reserved for enumerator members.
& Reserved for wrapped things.
' Reserved for datetime.
( unused
) unused
* Reserved for regular expressions.
+ unused
, unused
- unused
. Reserved for type.
/ Reserved for closures.