Yes, if you can come up with any of the following:

 * [deterministic finite automaton](https://en.wikipedia.org/wiki/Deterministic_finite_automaton) (DFA),
 * [nondeterministic finite automaton](https://en.wikipedia.org/wiki/Finite_automaton) (NFA),
 * [regular expression](https://en.wikipedia.org/wiki/Regular_expression#Formal_language_theory) (regexp of formal languages) or
 * [regular grammar](https://en.wikipedia.org/wiki/Regular_grammar)

for some language $L$, then $L$ is regular. There are [more equivalent models](https://en.wikipedia.org/wiki/Regular_language#Equivalence_to_other_formalisms), but the above are the most common.

Just to complete the list: 
$L$ will be also regular if 

 * it is finite,
 * you can construct it by performing certain operations on regular languages, and those operations are [closed for regular languages](https://en.wikipedia.org/wiki/Regular_language#Closure_properties), such as
      * intersection,
      * complement,
      * homomorphism,
      * reversal

  and [more](http://cs.stackexchange.com/questions/tagged/regular-languages+closure-properties), or
 * using [Myhill–Nerode theorem](https://en.wikipedia.org/wiki/Myhill%E2%80%93Nerode_theorem) if the number of equivalence classes for $L$ is finite.