themselves · pronoun /ðəmˈselvz/
themselves (REFLEXIVE)
A2 the reflexive form of the pronoun "they"
Dictionary examples:
Did they enjoy themselves at the theater?
They asked themselves where they had gone wrong.
Learner example:
They helped themselves [to] some fruit and sweets. (Key English Test; A2; Farsi)
(by) themselves
A2 alone or without anyone else's help
Dictionary examples:
The kids arranged the party all by themselves.
They did the catering themselves.
They've decided to run the club themselves.
Learner example:
Most people in Hong Kong do not make brea[k]fast themselves. They like eat[ing] out. (Skills for Life (Entry 2); A2; Czech)
themselves (EMPHASIS)
B2 used to emphasize the pronoun "they" or the particular group of people you are referring to
Dictionary examples:
The staff themselves were unhappy with the decision.
They themselves had no knowledge of what was happening.
Learner example:
Many times they think they themselves [have taken] part in a car race. (First Certificate in English; B2; Greek)