Looking for a free monolingual english dictionary like oxford or longman dictionary, but which I can freely use, without violating any intellectual property. I want to use it in my iOS app.

I need definition /meaning of english words expressed with simpler words. Any idea?


The English Language & Usage stackexchange site has a question with answers related to your question

What's the largest open-source dictionary that includes brief definitions of each word?


The popular answer is WordNet from Princeton. You can either browse or download the full data set, although it's about 10 years old.

The license allows commercial use.

Here is an example of the page for Data:


And the definitions

S: (n) data, information (a collection of facts from which conclusions may be drawn) "statistical data"

S: (n) datum, data point (an item of factual information derived from measurement or research)

  • In Oxford I can find definitions like prospects: chances or opportunities for success or wealth, wordnetweb contains no such a compact definition, only synonym, wordnetweb does seems not so professional
    – János
    Feb 2 '15 at 18:46

Wiktionary is the Wikimedia project's dictionary. Here is an example of a page, although the definitions are still quite technical:


Additionally, like simple.wikipedia, there is a Simple English Wiktionary page. Here is an example:


The definition you are looking for:

Data is information, such as facts, numbers, photographs, etc.

The license is GNU Free Documentation License (text).


All the Wikimedia projects use the same data dump scheme (backup index).

The Simple Wiktionary line looks like this:

2014-12-12 20:44:20 simplewiktionary: Dump complete

And the most recent link is:


From this page, you are looking for the top files:

Articles, templates, media/file descriptions, and primary meta-pages, in multiple bz2 streams, 100 pages per stream

The index file (simplewiktionary-20141212-pages-articles-multistream-index.txt.bz2, 144 KB) contains a listing of all the pages. Here are some randomly selected records:

enter image description here

You can use these words to then find definitions from the pages. I extracted the XML dump and put on pastebin the data for the page "Data" - LINK. The part you are looking for can be parsed out from these lines:

#{{uncountable}} '''Data''' is [[information]], such as [[fact]]s, [[number]]s, [[photograph]]s, etc.
#: ''A [[study]] using [[experiment]]al '''data''' from ten schools found no [[difference]] between [[method]]s.''


Here are some instructions on how to import the XML data dump - LINK.

Some possible tools, depending on your skills:

  • xml2sql (multiplatform C tool)

  • Pywikibot (Python, requires registering your app, but doesn't require reconstructing database)

  • mwdumper (Java)

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