Дождь испортил наши планы.

Because дождь is in the nominative case, which is the normal case for the subject of a Russian sentence.

In Дождь испортил наши планы, the structure is:

• дождь = the thing doing the action
• испортил = ruined
• наши планы = our plans

So literally, it is Rain ruined our plans.

Дождь is masculine.

One clue is the verb form испортил. In the past tense, Russian verbs agree with the subject in gender and number:

• masculine: испортил
• feminine: испортила
• neuter: испортило
• plural: испортили

Since the sentence says дождь испортил, the subject must be masculine singular.

Also, many nouns ending in a soft sign ь can be either masculine or feminine, so you often have to learn the gender individually. Дождь happens to be masculine.

Испортил is the past tense, masculine singular form of испортить.

It matches дождь because Russian past tense verbs agree with the subject:

• дождь испортил = the rain ruined
• буря испортила = the storm ruined
• море испортило = the sea ruined
• дожди испортили = the rains ruined

So the ending -л here shows a masculine singular past form.

This is about aspect, which is very important in Russian.

• портить = imperfective
• испортить = perfective

Испортил shows a completed action with a result: the rain ended up ruining the plans.

That fits this sentence well, because the idea is that the plans were spoiled as a result of the rain.

Compare:

• Дождь испортил наши планы.
  The rain ruined our plans. / The rain has spoiled our plans.

• Дождь портил наши планы.
  The rain was spoiling our plans / used to spoil our plans.
  This sounds more like an ongoing or repeated process, not a single completed result.

Because наши планы is the direct object of the verb испортил.

The verb испортить takes a direct object in the accusative case.

Here:

• singular: план
• plural: планы

For inanimate plural nouns, the accusative form is the same as the nominative form. So:

• nominative plural: планы
• accusative plural: планы

The adjective/pronoun наши agrees with планы in number, gender, and case.

So наши планы means our plans as the object of the verb.

Because планы is plural and inanimate.

In Russian, for many inanimate nouns, the accusative looks like the nominative. This is especially noticeable in the plural.

Compare:

• Я вижу наши планы. = I see our plans.
• Наши планы изменились. = Our plans changed.

In both cases, планы looks the same.

But with animate masculine plural nouns, accusative usually matches the genitive instead. For example:

• nominative: наши друзья
• accusative: наших друзей

So планы stays unchanged because it is inanimate.

Because Russian does not have articles like English a/an and the.

So Дождь испортил наши планы can be understood from context as:

• The rain ruined our plans
• Rain ruined our plans

Usually, context tells you whether the meaning is more definite or more general.

Yes. Russian word order is flexible because case endings show the grammatical roles.

The neutral order here is:

• Дождь испортил наши планы.

But you could also say:

• Наши планы испортил дождь.
• Испортил наши планы дождь.

These versions still mean basically the same thing, but the focus changes.

For example:

• Дождь испортил наши планы.
  Neutral statement.

• Наши планы испортил дождь.
  Emphasis on our plans or on what ruined them.

• Испортил наши планы дождь.
  More literary or emphatic.

So English relies more on word order; Russian often uses endings plus word order for emphasis.

Yes, but that would mean the rains or periods of rain ruined our plans, not just one instance of rain.

Notice the changes:

• дождь испортил = singular masculine
• дожди испортили = plural

The verb changes to испортили to agree with the plural subject.

So:

• Дождь испортил наши планы. = Rain / the rain ruined our plans.
• Дожди испортили наши планы. = The rains ruined our plans.

Дождик is a diminutive form of дождь.

• дождь = rain
• дождик = little rain, a bit of rain, or a more affectionate/light way to say rain

So:

• Дождь испортил наши планы. sounds neutral.
• Дождик испортил наши планы. can sound lighter, more conversational, or slightly ironic depending on context.

A learner should usually start with дождь, because it is the basic word.

Yes, дождь is a tricky word for many English speakers.

A rough guide:

• it sounds approximately like dozhd’
• the final ь is a soft sign, so it does not make its own sound, but it softens the final consonant

What makes it difficult is the consonant cluster жд and the soft ending.

A practical learner tip: listen to native audio and imitate it as a whole word, rather than trying to pronounce each letter too separately.

Also remember that the spelling is important even if fast speech may simplify the cluster somewhat.

Not exactly. Дождь specifically means rain.

If you want to say The weather ruined our plans, you would say:

• Погода испортила наши планы.

Notice that погода is feminine, so the verb changes to:

• испортила

So:

• Дождь испортил наши планы. = The rain ruined our plans.
• Погода испортила наши планы. = The weather ruined our plans.

Often, yes, but its exact force depends on context. Испортить can mean:

• to ruin
• to spoil
• to mess up

In this sentence, ruined is a very natural translation because the idea is that the plans were negatively affected and could not happen as intended.

In other contexts, испортить can be used more lightly:

• испортить настроение = to spoil the mood
• испортить праздник = to ruin/spoil the holiday
• испортить одежду = to ruin clothes

So the core idea is to make something worse, spoiled, or unusable.