Lentolippu ja varausvahvistus ovat puhelimessa, mutta kirjoitan myös ajan muistiin.

Because the subject has two parts: lentolippu ja varausvahvistus = the flight ticket and the booking confirmation.

In Finnish, when two singular nouns are joined by ja and together form the subject, the verb is usually plural:

• Lentolippu ja varausvahvistus ovat...
• not ...on

So even though each noun is singular by itself, together they make a plural subject.

Because the speaker means one flight ticket and one booking confirmation.

Finnish does not make the nouns plural just because there are two different things connected by ja. Each noun stays in whatever number it needs individually.

So:

• lentolippu = one flight ticket
• varausvahvistus = one booking confirmation

If there were several of each, you would use plurals such as lentoliput and varausvahvistukset.

Yes. Finnish uses compound words very heavily.

• lentolippu = lento
  • lippu
    literally something like flight-ticket
• varausvahvistus = varaus
  • vahvistus
    literally booking-confirmation

This is very normal in Finnish. English often writes such things as two words, but Finnish often combines them into one.

Puhelimessa comes from puhelin + -ssa/-ssä, the inessive ending, which usually means in.

So literally, puhelimessa means in the phone.

But in natural English we usually say on the phone when something is stored there. Finnish often uses an inside-location form where English prefers on.

So:

• puhelimessa = in/on the phone
• in this sentence: stored on the phone

This does not mean while talking on the phone here. The context clearly shows it means the ticket and confirmation are saved on the device.

Finnish often leaves out possessive words like my, your, or his/her when the meaning is obvious from context.

So puhelimessa can naturally mean:

• in the phone
• on the phone
• often, in context, on my phone

If the speaker wanted to be more explicit, they could say something like:

• puhelimessani = in my phone / on my phone

But in everyday Finnish, leaving that out is very common.

Because Finnish has no articles equivalent to English a/an and the.

So Finnish simply says:

• lentolippu
• varausvahvistus
• puhelimessa
• ajan

Whether something is understood as a or the depends on context.

In this sentence, the context makes the nouns specific, so English naturally translates them with the:

• the flight ticket
• the booking confirmation
• the phone
• the time

Finnish has no separate future tense like English will write. Very often, Finnish uses the present tense to talk about the future when the meaning is clear from context.

So:

• kirjoitan literally = I write
• but in context it can mean I’ll write or I’m going to write

Here, mutta kirjoitan myös ajan muistiin means something like:

• but I’ll also write down the time
• or but I’m also writing down the time

The exact English wording depends on what sounds natural in context.

Because ajan is the object form here.

The basic dictionary form is:

• aika = time

But after kirjoitan in this sentence, time is the direct object: the speaker is writing down a specific complete piece of information. In Finnish, that often gives the noun the total object form, which in the singular often looks like the genitive:

• aika → ajan

So:

• kirjoitan ajan muistiin = I write down the time

If you used aika, that would not be correct here.

Yes, it can.

That is a very common point of confusion:

• ajan can be the object form of aika = time
• ajan can also be the 1st person singular of ajaa = I drive

Context tells you which one it is.

Here, because it comes after kirjoitan and before muistiin, it clearly means the time, not I drive.

Muistiin comes from muisti = memory.

The ending -in here is the illative, which often means into.

So muistiin literally means into memory.

But in this sentence it is part of the common expression:

• kirjoittaa muistiin = to write down, to note down

So you should learn muistiin here mainly as part of that whole phrase.

Yes, very much so.

It is a standard Finnish expression meaning:

• write down
• make a note of
• note down

Literally it is something like write into memory, but you should think of it as an idiom.

Other similar verbs can also be used with muistiin, for example:

• merkitä muistiin = to note down
• panna muistiin = to put down / note down

Myös means also, too, or as well.

In this sentence:

• mutta kirjoitan myös ajan muistiin

it shows that, in addition to having the ticket and confirmation on the phone, the speaker will also do something else: write down the time.

Its position affects what feels most emphasized.

Here, myös is placed before ajan, but it naturally applies to the whole action:

• I’ll also write down the time

A different placement can slightly shift the focus. For example:

• Kirjoitan ajan myös muistiin
  can sound more like I’ll write the time down as well
• Myös minä kirjoitan ajan muistiin
  would emphasize I also write it down

So the word order is flexible, but the emphasis changes.