1. That may be combined.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• combineable,
• xombinable,
• vombinable,
• fombinable,
• dombinable,
• cimbinable,
• ckmbinable,
• clmbinable,
• cpmbinable,
• c0mbinable,
• c9mbinable,
• conbinable,
• combinablle,
• combinablee,
• combinible,
• combineble,
• combinatry,
• combinatee,
• combindly,
• comminable

• combination,
• coin bank,
• combinative,
• combinatory,
• convinced,
• combinational,
• confined,
• combined,
• confines,
• combine,
• convincible,
• communicable,
• combining,
• combinatorial,
• convince,
• combing,
• abominable,
• commutable,
• confine.

The adjective form of the word "combinable" is "combinable".

The plural form of the word "combinable" is "combinables".

The singular form of the word "combinable" is "combinable". It is the same in both singular and plural forms.