Yes, unless you are speaking telepathically. The spell works fine with Telepathy. 

Quote from SithLordFather >>

So I have a question. Can this be used on an opponent to make them drop their weapons in the middle of a fight? Or go prone in the middle of a fight? I've got one DM that believes it's a magic spell and doesn't cause them to cause themselves direct harm so should be allowed, and another DM that says they know they will be attacked if they go prone or drop their weapons so it cant be used mid fight. Essentially making this spell null and void for fighting purposes. 

 A consequence is not direct harm. So this should work fine. commanding a person to 'strike' the soldier they are talking to works fine, since striking the soldier does not directly harm the target. The fact that the soldier will definitely hit back is not relevant. 

command them to "lick." You'll really annoy the nearest character/monster but it's be worth it.

Why does this spell fail against undead?

The verbal component plucks the magical filaments of the universe and sets the weave of magic into motion like a ripple in a pond as a rock is droped into it. The target need not hear the command as the magic compells the target. The magical energy transfers through the weave not through vibrations of molecules like sound does.

Wouldn't being unconscious make them unable to act?  According to the write up, if the target can't perform the act the spell fails.  Maybe I reading it wrong.  Either way the DM has the last say.  So at your DMs table you can command an unconscious target.  Good way to get your downed fighter to safety, or sleep walk a target out of the room.

I have seen on other websites that bards also have access to this spell is that information wrong?

I like the command "betray"

It doesn't say the target has to hear you, only understand your language.

I made a Bard character and I have purchased Tasha's Cauldron, but it still won't allow me to add this spell to my bard's spell list. Not sure what setting I have missed.

What if I said: Suicide!

Quote from TyReg >>

Am i correct that in every option the target does NOT use their action?

because it is only mentioned in Halt, that it takes no action, but in the others its written, that it has to end its turn directy afterwards.

 

 

Beyond 20

 

 

 

 

 

 The spell forces the person to spend their turn carrying out the command. (Drop, Flee, and Grovel also use a turn -- the only example given that could possibly result in an additional action is Approach)

However, if the command is vague or leads room for misinterpretation by the target, the DM (or even a PC if they're the one targeted) has leeway for interpretation.

”The spell has no effect if the target is undead, if it doesn't understand your language, or if your command is directly harmful to it.“

Quote from Hamsandwitch23348 >>

What if I said: Suicide!

 command cant be directly harmful

This spell becomes more powerful the more languages you know in real life

I think it would be neat to drop "believe" or something along those lines to get advantage on a persuasion roll.

I know I'm replying to an old post, but it has a duration of one round. Your DM was very generous in letting you completely remove enemies from full encounters. 

So we ended last session half way through an encounter where our barbarian has had dominate person cast on him by what we think is a homebrew version of a lich. If I were to cast Command on the barbarian to attack the lich how is this going to interact with Dominate Person? I understand it will be DM discretion but I'm interested to hear people's interpretation.

I prefer to say Fall  instead of grovel.

I'm surprised no one here has suggested my favourite use for an upcast Command: Huddle, Crowd, Gather etc

Group them up, waste their turns, and then hit them with an AOE