1. A method for query suggestion performed by a processor executing computer-executable instructions stored on a memory device, the method comprising: for an input query in source language, identifying a query in target language from a query log of a search engine, the query in target language and the input query in source language having a cross-lingual similarity, the identifying the query in target language from the query log comprising: providing a plurality of candidate queries in target language; evaluating the plurality of candidate queries in target language at least partly by deducing a monolingual similarity between the input query in source language and a translation of a respective candidate query from target language to source language; and ranking the plurality of candidate queries in target language using a cross-lingual query similarity score, the cross-lingual query similarity score being based on a plurality of features and a weight of each feature in calculating the cross-lingual query similarity score; and suggesting the query in target language as a cross-lingual query at least partly based on click-through information of documents selected by users for the query in target language.