Freelang Dictionary is a free program for Windows. It is very easy to install and use: after installation, select a language from the list. Then you can download it and add it to the program. 
After installing the main Freelang application, you can download and install as many languages as you want. The program allows you to browse the lists, search for a word, add or modify an entry, and learn new words from a personal learning list.
All keyword lists are bilingual (from and to English). The application also has other combinations (such as from and to French or from and to Spanish). The program runs on all versions of Windows. It is free, but the lists are copyrighted to their authors.
If you cannot download a dictionary or want to evaluate it first, you can use the online version (works for all platforms: Mac, Linux...).
Currently, there are 270 dictionaries available. These include Greek.
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- Greek-English dictionary on the online language portal bab.la
- G. Babiniotis – Small Dictionary of Modern Greek for iPhone
