jīnwǎn wǒ yòng xǐyījī.

In Mandarin, time words often come near the beginning of the sentence, before the main action.

So 今晚我用洗衣机 is a very normal order:

• 今晚 = tonight
• 我 = I
• 用 = use
• 洗衣机 = washing machine

A very common pattern is:

Time + Subject + Verb + Object

So this sentence follows a standard Mandarin word order.

You could also say 我今晚用洗衣机, and that is also natural. Putting 今晚 first gives a little more focus to the time.

用 means to use.

In this sentence, it shows that the speaker is using the washing machine.
A very basic pattern is:

用 + tool / object

Examples:

• 用手机 = use a phone
• 用电脑 = use a computer
• 用洗衣机 = use a washing machine

So 用洗衣机 means use the washing machine.

Because in natural Mandarin, 今晚我用洗衣机 often sounds like something has been left out.

A native speaker would very often say:

• 今晚我用洗衣机洗衣服。 = Tonight I’m using the washing machine to wash clothes.

Without 洗衣服, the sentence can still work if the context is clear, but by itself it may sound slightly unfinished, like:

• Tonight I’m using the washing machine...
  and the listener expects for what?

So grammatically it can be understood, but in everyday speech a fuller sentence is often more natural.

Yes. 今晚 usually refers to tonight / this evening, depending on context.

It is a short and common way to talk about the evening of the current day.

A related expression is:

• 今天晚上 = this evening / tonight

These are very close in meaning.
今晚 is shorter and very common in speech.

Not necessarily.

Mandarin often does not mark tense the way English does. Time is often understood from a time word like 今晚.

So:

• 今晚我用洗衣机。

can already mean:

• Tonight I’ll use the washing machine
• Tonight I’m using the washing machine

If you want to make the future idea more explicit, you could say:

• 今晚我要用洗衣机。 = Tonight I want to / am going to use the washing machine.
• 今晚我会用洗衣机。 = Tonight I will use the washing machine.

But with 今晚, extra future markers are often unnecessary.

Mandarin does not use articles like English a and the.

So 洗衣机 can mean:

• a washing machine
• the washing machine

The exact meaning depends on context.

That is normal in Chinese. Many nouns appear without any article at all.

Yes. It is a compound word:

• 洗 = wash
• 衣 = clothes
• 机 = machine

So 洗衣机 literally means something like clothes-washing machine.

This is very common in Chinese: many words are built from meaningful parts.

洗衣机 is pronounced xǐ yī jī.

The tones are:

• 洗 xǐ = 3rd tone
• 衣 yī = 1st tone
• 机 jī = 1st tone

So the full word is:

• xǐyījī

A rough pronunciation guide:

• xǐ sounds a bit like shee with a dipping tone
• yī sounds like ee with a high level tone
• jī sounds like jee with a high level tone

Also, x in pinyin is not the English x sound. It is a soft sound made with the tongue close to the roof of the mouth, somewhat similar to sh, but lighter and more fronted.

Yes. That is perfectly natural.

• 今晚我用洗衣机
• 今天晚上我用洗衣机

These mean almost the same thing.

今晚 is shorter and more compact.
今天晚上 is a little fuller and sometimes clearer for beginners.

Sometimes, yes.

If the context already makes it clear who is speaking about themselves, you might hear:

• 今晚用洗衣机。

But on its own, that sounds a bit abrupt and context-dependent.

Mandarin often drops subjects when they are obvious, but in a simple learner sentence, keeping 我 is better and clearer.

Usually, no.

You normally just say 今晚, not 在今晚, in a sentence like this.

So:

• 今晚我用洗衣机。 = natural

But:

• 在今晚我用洗衣机。 = unnatural in most everyday contexts

The preposition 在 is not usually needed before a simple time word like 今晚 when it functions as the time of the action.