Konev je plná dešťové vody.

A word-for-word breakdown is:

• konev = watering can
• je = is
• plná = full
• dešťové vody = of rainwater / literally of rain water

So the whole sentence means The watering can is full of rainwater.

Because plný is an adjective, and in Czech adjectives must agree with the noun they describe.

Here, the noun is konev, which is:

• feminine
• singular
• nominative

So the adjective must also be feminine singular nominative:

• masculine: plný
• feminine: plná
• neuter: plné

That is why you get konev je plná.

Konev is a feminine noun, even though it ends in a consonant.

In Czech, not all feminine nouns end in -a. Some feminine nouns have a consonant ending, for example:

• konev = watering can
• dlaň = palm of the hand
• noc = night

So you simply have to learn konev as a feminine noun. That is why the adjective is plná.

Because after plný / plná / plné meaning full, Czech normally uses the genitive case.

So:

• voda = water (dictionary form, nominative)
• vody = of water (genitive singular)

This is the same idea as English full of water. In Czech, the of water part is shown by case, not by adding a separate word like of.

So:

• plná vody = full of water

Because dešťové is an adjective describing vody, and adjectives must agree with the noun they modify.

The basic phrase is:

• dešťová voda = rainwater / literally rain water

But in the sentence, voda has to be in the genitive after plná, so the whole phrase changes:

• nominative: dešťová voda
• genitive: dešťové vody

So both words change together.

No. Here vody is genitive singular, not plural.

This can confuse learners, because vody can look like a plural form in other contexts. But in this sentence, after plná, it is understood as singular:

• voda = water
• plná vody = full of water

Since water is a mass noun, singular makes sense here.

Yes. That is perfectly natural and means The watering can is full of water.

Adding dešťové makes it more specific:

• Konev je plná vody. = The watering can is full of water.
• Konev je plná dešťové vody. = The watering can is full of rainwater.

So the longer sentence just gives more information about what kind of water it is.

Yes. Czech often uses an adjective + noun phrase where English uses a single compound noun.

So:

• dešťová voda literally = rain water
• natural English translation = rainwater

That structure is very common in Czech.

In normal standard Czech, no.

Czech usually keeps the present tense of být (to be) in sentences like this:

• Konev je plná. = The watering can is full.

So je is the normal and expected form here. Leaving it out would sound nonstandard, very compressed, or stylistically unusual.

Because Czech has no articles.

English says:

• a watering can
• the watering can

Czech just says:

• konev

The exact meaning depends on context. So Konev je plná dešťové vody could mean:

• The watering can is full of rainwater
• A watering can is full of rainwater

In most real situations, context tells you which one is intended.

The given order, Konev je plná dešťové vody, is the most neutral and natural one.

Czech word order is more flexible than English, so other orders are possible, but they usually change the emphasis. For example:

• Konev je plná dešťové vody. = neutral
• Plná dešťové vody je konev. = marked, unusual, emphasizes watering can

For a learner, the original version is the best model to use.

No. Konev means watering can.

A few similar-looking words are:

• konev = watering can
• konvice = kettle / teapot / coffee pot, depending on context

So in this sentence, konev is definitely a watering can, not a kitchen kettle.