Où
Où asks for a place: in Où est-ce que c'est ?, it means “where.” Use it at the start of a question when asking where an object or place is.
est-ce que
In Où est-ce que c'est ?, est-ce que is the question-marking construction that introduces the question. The parts est-ce and que work together here; the same construction appears in Quand est-ce que tu viendras ?.
c'est
In Où est-ce que c'est ?, c'est means “it is” and identifies the thing whose location is being asked about. It is the contraction of ce and est; the complete pattern Où est-ce que c'est ? asks where something is.
Tu
Tu addresses one person as “you” in Tu es où ?; it is the familiar or informal singular form. It commonly appears before the verb when speaking directly to that person.
es
In Tu es où ?, es means “are” with tu and describes the person’s current location. It is the tu form of être and is used after tu in statements or questions about that person.
Qu'est-ce qui
In Qu'est-ce qui s'est passé ici ?, Qu'est-ce qui asks what thing or event occurred. Qu'est-ce introduces “what,” and qui connects that “what” to the verb as the thing that happened; together they form one question construction. Use Qu'est-ce qui before a verb when asking what caused or underwent an event.
s'est
In s'est passé, s'est is the se + est part of the expression for an event that occurred; it does not by itself carry the whole meaning “happened.” Together with passé, it forms s'est passé, meaning “happened” in this dialogue. Reuse the complete expression when asking what occurred.
passé
In Qu'est-ce qui s'est passé ici ?, passé completes s'est passé, which means “happened” or “occurred.” It is the past-participle form related to passer, so learn it here as part of s'est passé rather than as a standalone translation. Use the full expression when asking what occurred.
ici
Ici means “here,” referring to the place where the event occurred. It can point to the speaker’s current location or another place being indicated; here it follows s'est passé in Qu'est-ce qui s'est passé ici ?.
Quelle
In Quelle heure est-il ?, Quelle means “what” or “which” before heure and takes its feminine singular form to agree with that noun. The pattern Quelle plus a feminine singular noun asks which or what one; here it asks for the time.
heure
In Quelle heure est-il ?, heure means “hour” and, in this question, refers to the current time. It is the noun used after Quelle in the common question for asking the clock time.
est-il
In Quelle heure est-il ?, est-il means “is it” and uses inversion, with est before il to form the question. This order is part of the complete expression for asking the time, so reuse Quelle heure est-il ? as a whole.
Quand
Quand means “when” and asks about the time or occasion of an event, as in Quand est-ce que tu viendras ?. It commonly begins a question about when something will happen or someone will come.
viendras
In Quand est-ce que tu viendras ?, viendras means “will come.” It is the future form used with tu and is related to the verb venir; the reusable pattern is tu viendras when asking or stating that one person will come.
Pourquoi
Pourquoi means “why” and asks for a reason, as in Pourquoi tu es en retard ?. It commonly comes at the beginning of a question asking why someone did something or is in a particular situation.
en
In en retard, en is part of the expression meaning “late”; it does not carry the whole meaning “late” by itself here. A common reusable pattern is être en retard, used when someone is late for an event or appointment.
retard
In en retard, retard contributes the idea of delay, and the full expression en retard means “late” in Pourquoi tu es en retard ?. It is commonly used after être to describe someone who is late, so learn the complete expression rather than translating retard alone as “late.”