[maris oren]

left hand opponent-pass. partner bid 1 diamond. right handed partner 1 spade. i have 6 HCP and 5 hearts. what do i bid?
If I had 10 HCP and 5 hearts

[smerriman]

With 10 HCP and 5 hearts you would bid 2♥.

Double here shows exactly 4 hearts, OR a hand with 5+ hearts that is too weak to bid 2♥.

(Obviously, it depends a bit on your shape / where your honors are located, since pass is an option too.)

[apollo1201]

Unless your 6 HCPs look like this, pass can seriously be considered as partner will really expect some kind of positive hand

x
QJTxx
Kxxxx
xx

And with 10 and 5H, unless they look like this where X is probably safer, 2H is ok but keeping in mind you’re minimum in case partner asks or invites later on

QJ
Jxxxx
Jxx
KQxx

Last, with 10+ and only 4H, you also X unless you have a natural forcing and more descriptive call (e.g. with 5C and 4H, 2C is better).