Fuente: April 2014 ACBL Bridge Bulletin 
If ever there was a game driven by logic, that game is bridge. And yet, the subject of rebidding a five-card suit sometimes seems to defy logic. The shining example is when opener starts with 1 and faces the question of whether to rebid 2, holding five clubs and a minimum opening.
«1 could be a three-card suit,» says a small voice. «Holding five clubs, what could possibly be wrong with rebidding to show extra length?» Sounds logical, right? Except that, in most cases, it is the wrong bid. This could cause headaches.
For instance, suppose you are dealt: K 8 10 9 2 A J 4 K J 7 6 3. You open 1, partner responds l . Many players would rebid 2, but nearly all experts would rebid 1NT. The club suit is decent and the heart stopper missing – both of which may suggest 2. However, 2 is a level higher than 1NT and in a lower-scoring strain. There is no assurance of a club fit if partner has a weak hand and passes. Even if partner has three clubs, 1NT may be a better contract than 2 when the clubs can be established.
Furthermore,1NT makes it easier for responder to explore the majors, where matchpoint gold is buried. If responder has 5-4 or 5-5 in the majors and a minimum hand, he will likely pass 2 because, absent special agreements, 2 is forcing in standard bidding. After opener’s 1NT rebid, however, 2 offers opener a pass-or-correct option. Conventions like new-minor forcing or checkback are available with invitational hands or better.
Hands with a six-card minor are much more likely to be appropriate for suit play than notrump. When responder has a game-going hand, knowing that he can expect opener to deliver a six-card minor helps assess the chances for a borderline 3NT.
When should a five-card minor be re-bid? As opener, I’d say only in an emergency, when other rebids look worse. Alter opener’s original hand slightly : K 8 2 92 A J 4 K J 763. After 1 -1; 2 seems clearly best. Three-card support with a high honor and a weak doubleton make 1NT less appealing. Responder should be aware that the raise doesn’t guarantee four. If the pair rests in 2 on a 4-3 fit, it may well be a better contract than 1NT, especially with a ruffing value in hearts. Also, 2 outscores 2 when both make.
Alter opener’s hand to: 9 8 2 72 A J 4 A Q J 6 5, and we have finally reached the tipping point where a rebid of 2 is probably best. 1NT and 2 are not very palatable, and the club suit has real quality. There are times when rebidding a five-bagger is indicated. If you open 1 or 1, the opponent overcalls 1, and responder bids 2, presumably showing at least a limit raise, your rebid of 3 or 3 doesn’t say anything about length; it is merely a signoff.
Playing two-over-one as game forcing, you open 1 holding: AK762 754 J7 KQ2, and partner responds 2. You are endplayed into rebidding 2, unable to raise, bid notrump, or show a second suit. At this stage of the auction, responder can’t determine whether opener holds extra spade length. (For some partnerships, 2NT would be the «default» action with this hand, so in their auctions, 2 would show at least six.)
There are situations where rebidding a five-card major is the preferred action. On the other side of the table, let’s say you hold: QJ1052 104 86 K872. Partner opens 1 , you respond 1 , and partner rebids 1NT. Here, passing 1NT is a big gamble. Even if partner has a high spade, your hand may be unreachable in notrump, while in a spade partial, your long trump suit will always be worth tricks. Rebid 2.
Another instance where rebidding a five-card major is good practice is after opener reverses, e.g., 1 -1 ; 2. Responder should strain to repeat a five-card major. This keeps the bidding low and makes it easy for opener to finish his description. After a reverse, opener promises one more bid. Responder’s priority to rebid a five-card major also adds clarity when responder rebids 2NT, strongly suggesting only four spades. If opener holds: Q76 AK95 AQJ862 —, rebidding a nonforcing 3 is clearly indicated. There is little need to worry that a 5-3 spade fit will be missed.