Malstreĉu la ŝraŭbingon per la ŝraŭbŝlosilo.

The ending -u is the Esperanto volitive ending. In a sentence like this, it gives a command or instruction: Loosen ...

So:

• malstreĉi = to loosen, slacken, relax
• malstreĉu = loosen! / please loosen

In practice, this is the normal form used for commands, requests, instructions, and directions.

mal- creates an opposite meaning.

Here:

• streĉi = to tighten, stretch, make taut
• malstreĉi = to loosen, relax, release tension

This is very common in Esperanto. English often uses a completely different word, but Esperanto often builds the opposite neatly with mal-.

The -n marks the direct object.

That means la ŝraŭbingon is the thing being acted on — the thing you are loosening.

Compare:

• Malstreĉu la ŝraŭbingon = Loosen the nut / threaded piece
• without -n, it would not be marked as the direct object

Also, -n does not mean plural. This word is still singular. If it were plural, it would be ŝraŭbingojn.

la is the Esperanto definite article, meaning the.

Esperanto has:

• la = the
• no separate word for a / an

So la ŝraŭbingon and la ŝraŭbŝlosilo mean that the speaker is referring to specific, identifiable things — the particular part and the particular tool relevant in the situation.

In practical instructions, this is very common.

per means by means of, using, or with the help of.

So:

• per la ŝraŭbŝlosilo = using the wrench/spanner/tool

This is different from kun, which means with in the sense of together with.

So:

• per la ŝraŭbŝlosilo = use the tool
• kun la ŝraŭbŝlosilo would sound more like being together with the tool, not using it as an instrument

This is an important distinction in Esperanto.

These endings are very useful Esperanto word-building pieces.

• -ilo = a tool or instrument used for doing something
• -ingo = a holder, socket, sheath, or receiving piece

So in this sentence:

• ŝraŭbŝlosilo is a kind of tool
• ŝraŭbingo is a kind of receiving/holding threaded piece

Even if you do not know the exact technical translation, the endings already tell you a lot about the role of each object.

Esperanto often builds words by combining meaningful parts.

A helpful rule is: the last part is the main idea, and the earlier part modifies it.

So:

• ŝraŭb-ingo = a kind of ingo related to a ŝraŭbo
• ŝraŭb-ŝlosilo = a kind of ŝlosilo related to a ŝraŭbo

This is one of the most characteristic features of Esperanto. Instead of using long phrases, it often makes compact compound words.

Yes, the subject is omitted because it is understood.

In commands, Esperanto often leaves out vi just like English leaves out you:

• Malstreĉu la ŝraŭbingon = (You) loosen the nut/piece

You could add vi for emphasis, but normally it is unnecessary.

No, not completely. The sentence uses a very normal, straightforward order:

• Verb + object + instrument phrase

Because Esperanto marks the direct object with -n, the word order can be changed more freely than in English.

For example, you could also say:

• Per la ŝraŭbŝlosilo malstreĉu la ŝraŭbingon.

That would still be understandable. But the original order is the most neutral and natural for an instruction.

A few pronunciation points:

• ŝ sounds like sh in ship
• ĉ sounds like ch in chair
• aŭ sounds roughly like ow in cow

So some parts are:

• ŝraŭ- ≈ shrow
• streĉu ≈ STREH-choo

A rough pronunciation of the whole sentence is:

mahl-STREH-choo lah shrow-BEEN-gon pehr lah shrowb-shlo-SEE-lo

Also, Esperanto stress is very regular: it falls on the second-to-last syllable of each word.

By itself, malstreĉu is simply the normal command/instruction form. It is not automatically rude.

Its tone depends on context:

• in a manual, it is just an instruction
• in conversation, it can be a direct request or command
• to sound softer, speakers may add words like bonvolu (please)

So the form itself is neutral; politeness comes from context and wording.