def simplify(penn_tag):
    """ Simplify Penn tags to n (NOUN), v (VERB), a (ADJECTIVE) or r (ADVERB)"""
    pre = penn_tag[0]
    
    if pre == 'J':
        return 'a'
    elif pre == 'R':
        return 'r'
    elif pre == 'V':
        return 'v'
    elif pre == 'N':
        return 'n'
    else:
        return 'r'
        return 'other'