Moram naoštriti nož prije večere.

Croatian usually drops the subject pronoun because the verb ending already shows the person/number. Moram clearly means (I) must / I have to, so ja is optional and only used for emphasis or contrast:

• Moram naoštriti nož. = neutral
• Ja moram naoštriti nož (a ti ne moraš). = I have to (but you don’t)

In everyday Croatian, morati commonly corresponds to have to / need to, and it can also be a strong must depending on context. It expresses obligation or necessity:

• Moram = I have to / I must
  Tone is often closer to English have to unless the situation makes it strict.

This is about aspect (completed vs ongoing).

• naoštriti is typically perfective: to sharpen (and finish sharpening / make it sharp)—a completed result.
• oštriti is usually imperfective: to be sharpening / to sharpen (as an ongoing process or habit).

Because the sentence is about doing it before dinner (a single completed task), perfective naoštriti is natural.

Nož is in the accusative singular because it’s the direct object of the verb (to sharpen what?). For many masculine inanimate nouns, accusative looks the same as nominative:

• nominative: nož
• accusative: nož

The preposition prije takes the genitive case.
Večera (dinner) becomes večere in genitive singular:

• prije večere = before dinner

They overlap in meaning but are used differently:

• prije + genitive = before in a time sense (earlier than): prije večere
• pred + instrumental = in front of (place) or sometimes shortly before (time, more immediate): pred večerom can suggest “right before dinner / just before dinner” or be more situational.

For a neutral “before dinner” (time), prije večere is the default.

Yes, you can. Croatian word order is flexible because cases mark roles. Different orders shift emphasis:

• Moram naoštriti nož prije večere. = neutral
• Prije večere moram naoštriti nož. = emphasizes the time constraint (before dinner)
• Nož moram naoštriti prije večere. = emphasizes the knife (as opposed to something else)

Often, yes, but the nuance changes:

• Moram = I have to (obligation/necessity)
• Trebam = I need / I should (more like need/requirement, sometimes softer)

Trebam naoštriti nož prije večere sounds more like “I need to sharpen the knife before dinner” (practical necessity), while moram can imply a stronger requirement.

Moram is 1st person singular present. The infinitive is morati. Present tense forms include:

• ja moram = I must
• ti moraš = you must
• on/ona/ono mora = he/she/it must This is why Croatian can omit ja—the form moram already signals “I.”