For the English learning beginners the small vocabulary is a rather common problem. It's not so important in spoken language, but when you write it becomes a real trouble, especially if you write something longer than short posts or comments. The same words, repeated in each and every sentences, or at least rather frequently - isn't a good style. Furthermore, it's kind of hard to read such texts and, of course, poor vocabulary articles doesn't give any trust.

So, for writing well quality articles we should use synonyms everywhere it's possible to prevent repeating words. For finding synonyms we can use a historical thesaurus of English (the largest thesaurus in the world). Although it's the best and right way, it isn't like an easy-to-use site, and if we plan to use it regularly it can be rather tiresome.

Fortunately, there are a lot of other Internet services, which can help us to find synonyms rather quickly. Here is the list of some of them (most popular and qualitative, from my point of view).

synonym.com

As for me, one of the best. It's simple and user-friendly. In most cases you find what you want.

thesaurus.com

More "serious" service than the previous one. Gives you dozens of additional information. Can be rather helpful if your goal is not only to find synonym quickly but to get some extra information too.

synonyms.net

Another simple and easy usable service. With more information than the first one, but not so over functional as the second one.

thefreedictionary.com

And another service, dictionary plus thesaurus.

You can choose one which you consider the most suitable especially for you, or use them all depends on situation and requirements.