Breakdown of ¡Entra en la casa ahora!
la casa
the house / home (also "at home")
en
in / on / by (means of transport) / about (after pensar)
ahora
now
entrar
to enter
Questions & Answers about ¡Entra en la casa ahora!
Why is it entra and not entras if I am telling "you" to enter?
When you give a positive command to someone you address as tú (informal singular "you"), you use the affirmative imperative. For regular -ar verbs like entrar (to enter), the rule is simple: just drop the -r from the infinitive. This makes entrar become entra. Notice that it looks exactly like the present tense form for él or ella.
How would I change this sentence to tell a group of friends to enter?
You would use the vosotros (plural informal "you") command form. For all regular verbs, you make this form by dropping the final -r from the infinitive and adding a -d. So, entrar becomes entrad, making the sentence ¡Entrad en la casa ahora!
Why do we need the word en here? In English, we just say "enter the house".
While English uses "enter" directly with the destination, Spanish requires a preposition. When you go into a place, you use entrar en (literally "to enter in") or sometimes entrar a. Without en, the sentence would sound incomplete to a Spanish speaker.
What is the upside-down punctuation mark at the beginning of the sentence?
That is an inverted exclamation mark (¡). In Spanish, any sentence or phrase that ends with an exclamation mark must also begin with an inverted one. This helps the reader know immediately that the sentence is an exclamation or a forceful command before they even finish reading it.