Broca's area

Broca's area is a part of the frontal lobe on one hemisphere (the person's dominant hemisphere - usually the left one in a right handed person) that is linked to speech production, language production and language comprehension. It was identified by French physician Pierre Paul Broca who noted that damage to the area was related to speech impairment. 
Individuals who have suffered damage in the area still may be able to speak and use appropriate words, but have difficulty forming sentences or using grammatical constructs such as conjunctions and helper verbs. However, it appears that slow damage to the area (such as a tumor) will minimally impair speech and it could be that the functions of the area can be transferred slowly over time. 
Broca's area at Wikipedia