Plantan þarf meira vatn.

Because plantan is the definite form, meaning the plant.

In Icelandic, the is usually not a separate word. Instead, the definite article is attached to the end of the noun.

• planta = plant
• plantan = the plant

So this sentence uses the definite noun: the plant.

Plantan is nominative singular.

It is nominative because it is the subject of the sentence, the thing doing the needing. It is singular because we are talking about one plant.

So grammatically:

• planta = nominative singular indefinite
• plantan = nominative singular definite

The dictionary form of the verb is þurfa, meaning to need.

Þarf is the present tense singular form used here with plantan.

A few present-tense forms are:

• ég þarf = I need
• þú þarft = you need
• hann/hún/það þarf = he/she/it needs
• við þurfum = we need

Since plantan is singular, þarf is the correct form.

Because vatn is a neuter noun, and meira is the neuter singular form used here.

In meira vatn, the word meira means more and matches vatn.

So:

• meira vatn = more water

This is the form you expect with a neuter singular mass noun like vatn.

No. Meira is used for amounts or uncountable nouns, while fleiri is used for countable plural items.

So:

• meira vatn = more water
• meira kaffi = more coffee
• fleiri plöntur = more plants
• fleiri bollar = more cups

Since water is not being counted as separate items, meira is the right choice.

Icelandic usually handles these two ideas differently from English:

• the is often attached to the noun: plantan = the plant
• a/an does not exist as a separate indefinite article in Icelandic

So vatn can simply mean water, and context tells you how specific it is.

That means:

• plantan = the plant
• vatn = water

It is in the accusative.

The verb þurfa normally takes an accusative object, so the thing needed goes into the accusative case.

Here, that thing is vatn.

A useful detail: for many neuter nouns, the nominative and accusative singular look the same. So even though vatn is accusative here, its form does not visibly change.

This is the normal, neutral word order:

• Plantan = subject
• þarf = verb
• meira vatn = object/what is needed

So the structure is basically:

subject + verb + object

That said, Icelandic is also a verb-second language in main clauses. That means the finite verb often comes in the second position.

In this sentence, that happens naturally:

• Plantan þarf meira vatn

If you begin with another element, the verb still tends to stay second:

• Núna þarf plantan meira vatn = now the plant needs more water

A rough English-friendly guide is:

• Plantan ≈ PLAN-tan
• þarf ≈ tharf, with th like in thin
• meira ≈ MAY-ra
• vatn ≈ VAHTN

A few pronunciation notes:

• þ is like English th in thin, not like th in this
• Icelandic words are usually stressed on the first syllable
• r is typically tapped or trilled more than in most English accents

So the whole sentence is roughly:

PLAN-tan tharf MAY-ra VAHTN