Sit down
The formal version of 'sit down', used with 'usted' to show respect to elders, strangers, or superiors.
The plural 'sit down', used when speaking to two or more people ('ustedes'). This is standard in all of Latin America.
A slightly softer, more polite alternative meaning 'take a seat'. This is the informal 'tú' version.
Please, sit down here. The chair is free.
Ma'am, please sit down. Would you like a glass of water?
Hi! Come in and take a seat.
Kids, sit down! The movie is about to start.
In countries that use 'vos' instead of 'tú', the command is 'Sentate' (sen-TAH-teh), with the stress on the second-to-last syllable.
For the informal plural ('vosotros'), the command is 'Sentaos' (sen-TAH-ohs). They still use 'Siéntense' for the formal plural ('ustedes').
Usage is standard. 'Siéntate' is for informal singular ('tú'), 'Siéntese' for formal singular ('usted'), and 'Siéntense' for all plural situations ('ustedes').
Saying 'Sienta' instead of 'Siéntate'. The verb is 'sentarse' (to sit oneself down), a reflexive verb. You must include the pronoun ('-te', '-se') to indicate the person is sitting themselves down.
Using the wrong formality. Saying 'Siéntate' (informal) to an authority figure or an elderly person is considered disrespectful. Use 'Siéntese' in formal situations.
Forgetting the accent mark. It's 'siéntate', not 'sientate'. The accent is required on command forms like this to maintain the original stress of the verb.
Using 'sentar' for 'feel'. The verb 'sentir' means 'to feel'. For example, 'Me siento mal' (I feel bad) vs. 'Me siento mal' (I sit poorly). Context is key, but be aware of the two different verbs.