In Modern American bidding, we define the minor suit openings to be more restricted than Standard American or 2/1 bidding systems.

Opening 1♣ shows 1 of 2 types of hands: - A balanced hand with 12-14 HCP (and no 5 card major). It may as few as 2 clubs in the hand and could have longer diamonds. This includes hands with 2 clubs and 5 diamonds, assuming no shortness in the major suit. - Or an opening hand (11-21 HCP) with a long club suit. A long suit is considered a 'rebiddable suit' as the opener will most likely need to rebid clubs after partner's response

Opening ♦ shows an unbalanced hand and at least 4 diamonds. If the hand doesn't have any singleton or void, then it must have 6 or more diamonds (6-3-2-2) or (7-2-2-2) shape. A 1♦ opening hand will have at least 11HCP and up to 21HCP.