Mér líkaði teið betur þegar ég setti kanil og engifer í það.

Because líka works differently from English to like.

In Icelandic, the person who experiences the liking is often in the dative case, not the nominative. So:

• mér = to me / for me
• líkaði = pleased / was pleasing

So Mér líkaði teið is literally closer to The tea pleased me, even though the natural English meaning is I liked the tea.

This is one of the most important patterns to learn with líka:

• Mér líkar teið = I like the tea
• Mér líkaði teið = I liked the tea

Líkaði is the past tense of líka.

The basic tense pattern is:

• líkar = likes / is pleasing
• líkaði = liked / was pleasing

Since the sentence talks about a past situation, Icelandic uses líkaði.

So:

• Mér líkar teið = I like the tea
• Mér líkaði teið betur = I liked the tea better

Teið is the noun te with the definite article attached, so it means the tea.

In Icelandic, the definite article is usually added to the end of the noun rather than written as a separate word.

• te = tea
• teið = the tea

The ending -ið is the definite article here.

It is nominative singular.

With líka, the thing that is liked is usually in the nominative, while the person who likes it is in the dative.

So in:

• Mér líkaði teið

we get:

• mér = dative
• teið = nominative

That may feel backwards to an English speaker, but it is normal with this verb.

Betur means better and is the comparative adverb of vel (well).

With líka, Icelandic often uses betur in the same way English says like something better.

So:

• Mér líkaði teið betur = I liked the tea better

Even though English uses better after liked, Icelandic is not using an adjective here; it is using the adverb betur in a very natural expression.

Related forms:

• vel = well
• betur = better
• best = best

Þegar means when in this sentence.

It introduces the time clause:

• þegar ég setti kanil og engifer í það = when I put cinnamon and ginger in it

So the whole sentence compares two situations and says the tea was more pleasing at the time when cinnamon and ginger were added.

Setti is the past tense of setja (to put).

Because the whole sentence is talking about a past situation, the verb inside the þegar clause is also in the past:

• ég setti = I put

So:

• þegar ég setti kanil og engifer í það = when I put cinnamon and ginger into it

They are the objects of setti.

In að setja eitthvað (to put something), the thing being put is a direct object, so it typically appears in the accusative.

• kanill is the dictionary form
• kanil is the accusative singular form used here

Engifer is one of those nouns whose form does not change here, so it stays engifer.

So:

• kanil og engifer = cinnamon and ginger

This is a very common Icelandic case pattern with prepositions.

The preposition í can take:

• accusative for movement/direction: into
• dative for location: in

Here, the sentence is describing putting something into the tea, so Icelandic uses the accusative:

• í það = into it

If it were describing something already being located in it, you would expect the dative:

• í því = in it

So this is a classic motion-versus-location distinction.

Það refers back to teið.

So:

• í það = into it
• it = the tea

Even though teið is neuter singular, það is exactly the pronoun you would expect, because það is the neuter singular form.

Icelandic follows the V2 rule in main clauses, which means the finite verb tends to come in the second position.

Here the first element is mér, so the finite verb líkaði comes next:

• Mér | líkaði | teið betur ...

This is perfectly normal Icelandic word order.

If another element were placed first, the verb would still usually stay second. That is a major feature of Icelandic sentence structure.

Possibly in a different style or context, but þegar alone is the normal and natural choice here.

It simply means when, and it smoothly connects the idea:

• I liked the tea better
• when I added cinnamon and ginger to it

So þegar is the straightforward everyday option.

Yes, betur implies a comparison.

The unstated comparison is something like:

• better than before
• better than without cinnamon and ginger
• better than it tasted otherwise

Icelandic often leaves that comparison understood from context, just as English does in I liked the tea better when...

So the sentence does not need to explicitly say than before for the meaning to be clear.