13. A computer program product for automatic cognate detection, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform: stemming a first word in a first language in a bilingual corpus to obtain a first stem and a second word in a second language in the bilingual corpus to obtain a second stem; calculating a probability for aligning the first stem and the second stem; normalizing the first stem and the second stem; calculating a distance metric between the normalized first stem and the normalized second stem identifying the first word and the second word as a cognate pair when the probability and the distance metric meet a threshold criterion; storing the cognate pair in a set of cognates; retrieving a candidate sentence in the second language from a corpus; filtering the candidate sentence by an active vocabulary of a user in the second language and the set of cognates; calculating a sentence quality score for the candidate sentence; and ranking the candidate sentence for presentation to the user based on the sentence quality score.
13. A computer program product for automatic cognate detection, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform: stemming a first word in a first language in a bilingual corpus to obtain a first stem and a second word in a second language in the bilingual corpus to obtain a second stem; calculating a probability for aligning the first stem and the second stem; normalizing the first stem and the second stem; calculating a distance metric between the normalized first stem and the normalized second stem identifying the first word and the second word as a cognate pair when the probability and the distance metric meet a threshold criterion; storing the cognate pair in a set of cognates; retrieving a candidate sentence in the second language from a corpus; filtering the candidate sentence by an active vocabulary of a user in the second language and the set of cognates; calculating a sentence quality score for the candidate sentence; and ranking the candidate sentence for presentation to the user based on the sentence quality score. 14. The computer program product of claim 13 , wherein the probability is calculated with a Viterbi algorithm.