Using better minor convention partner open one club, and I have five diamonds with three honors. I answer two diamonds to show the diamonds. Is this correct?
No, playing a natural system such as Goren or Two Over One the jump shift response into a new suit shows about 17-18 points in addition to the good suit. You have the good suit but (at time of writing) not the requisite overall hand strength. If the suit being bid is not at least 5 cards in length then the bid must also show 4+ card support in Opener's suit..
In addition to the above the bid announces that:
- The opponents shall not be allowed to play undoubled;
- Slam will be bid if a fit is found and sufficient controls are present.
It is because of the first point above that the bid should be made on HCP rather than playing strength. Good suits with playing strength but less defence can make a delayed jump shift, a delayed jump raise, or a delayed jump rebid. These now deny sufficient defensive strength for the initial jump shift. The jump shift response must never be made with a two suited hand unless the second suit is Opener's first bid suit.
When partner opens 1C it is very likely (especially playing a Strong 1 NT) that partner intends to rebid either 1 or 2 NT. Narrowing the jump shift response to slam going hands leaves more room for additional exploration below game, which will not only improve any NT games stumbled into but also find more good minor suit slams.
Playing Standard American or Two-over-one the classic agreement is to play strong jump shifts in a non-competitive auction. In that case a 2D bid after a 1C opening would show not only a 5-card suit including at least 5 HCP, but also at least 17 points in the overall hand. Such a bid is forcing to game.
However, many of the stronger players now prefer to play Weak Jump Shifts in which a bid of 2D over an opening 1C would show a 6-card suit, and 2-5 HCP in the total hand. Over such a bid, opener usually passes or bids the final contract. A bid of 2NT is forcing and asks the responded to further describe his hand.
Playing SA or 2/1, a bid of 1D over 1C often indicates a 5-card suit. With a 4-card or longer major, the responder will usually bid the major unless the diamonds are significantly better, and the hand is strong enough to reverse by bidding the major later. Therefore only hands which are 3-3 or shorter in the majors (or rather strong hands) will bid 1D. Many (but far from all) such hands have 5+ cards in the diamond suit. Therefor opener should be prepared for a 5-card diamond suit, and responder does not need to jump to show it, unless the hand suits the partnership agreement for a jump-shift, weak or strong. If the bidding has gone 1C-pass-1D, the responder will probably rebid Diamonds later to show such a good suit as 5-cards with three honors. Remember that as a new-suit bid from an unpassed responder, 1D is forcing 1 round.
To anyone thinking that "Standard American" should include 4-card major systems, and so this answer should have discussed such alternatives: that was once the case, but has not been for several decades. No North American tournement or club player describing a system as "Standard American" will mean a 4-card major system. This has been true since not long after the final edition of Goren's Bridge Complete came pout in the early 1980s with the Goren system fully reworked on a 5-card major basis. There is a case to eb made that a 4-card major system is better in many cirumstsancecs. But what ever one might call such a system, it isn't "Standard American" (much less SAYC), and it isn't common in NA duplicate play.