Some Icelandic infinitives end with a -ja suffix. These verbs can be conjugated like -ur verbs, with the suffix lost in the first person singular. When conjugating -ja verbs, the single "j" must be removed, so "syngja" ('to sing') would become "ég syng" ('I sing') in the first person singular and not "ég syngj" (and "syngja" is a strong verb (past tense "söng"), so irregularities are to be expected). The j in itself is not a reliable indicator. Examples could be "emja" ('squeal'), which belongs to one class (singular, first person, "ég emja", past tense "ég emjaði") versus "telja" ('count'), belonging to another class, ("ég tel", past tense "ég taldi").