Learn Hardcore Icelandic: Ég var næstum búin að gleyma töskunni.

Female speaker: Ég var búin …
Male speaker: Ég var búinn …
Neuter is used with neuter subjects like það: Það var búið … In the plural you get búnir (masc./mixed), búnar (fem.), búin (neut.).

What does the construction “vera búinn að + infinitive” express?

It’s a very common resultative/perfect-like construction meaning “to be finished with/have done” something by a reference time. With the past of “vera” (var), it corresponds to a past perfect-like sense (“had done”). Here, it conveys that at that past time you were (almost) at the point of having completed the forgetting.

Why is it “var” and not “er”?

Var is the past tense of vera (“to be”). It places the situation in the past. If you’re talking about the present, you would use er: for example, a present-time version would be “Ég er næstum búin(n) að …”

Can a man say this sentence as-is?

He must use the masculine agreement: Ég var næstum búinn að gleyma töskunni.

Where should “næstum” go? Could I say “Ég var búin að næstum gleyma …”?

Place næstum right before the phrase it modifies. The natural placement here is before the “vera búinn (að …)” unit:

Preferred: Ég var næstum búin(n) að gleyma … “Ég var búin að næstum gleyma …” is not idiomatic. You can also move “næstum” in a simple past sentence: Ég næstum gleymdi …

Could I just say “Ég gleymdi töskunni”? How does that differ?

Yes. Ég gleymdi töskunni states that the forgetting actually happened. By contrast:

Ég var búin(n) að gleyma … = it had already happened by some past point.
Ég var næstum búin(n) að gleyma … = it almost happened (but didn’t).

Why is it “töskunni” (dative) and not “töskuna” (accusative)?

Because the verb gleyma (“to forget”) governs the dative case for the thing forgotten. So you say:

gleymdi töskunni (dat.) not ✗gleymdi töskuna (acc.).

How do we get from “taska” to “töskunni”?

Step by step:

Base noun: taska (bag), feminine.
Dative singular (indefinite): tösku (u-umlaut turns a → ö; see next Q).
Add the definite article for dative singular feminine: -nni.
Result: töskunni = “the bag” (dative singular definite).

Why does the vowel change from “a” to “ö” (taska → tösku/töskunni)?

That’s u-umlaut: in many words, an “a” changes to “ö” when a following syllable contains a “u”. So:

taska → dative sg. tösku → dative sg. definite töskunni.

What is the role of “að” before “gleyma”? Can I drop it?

Að is the infinitive marker (“to”). In the construction vera búinn að + infinitive, you must include að:

Ég var búin(n) að gleyma … (correct)
✗Ég var búin(n) gleyma … (incorrect)

Is “gleyma” used both for “forget something” and “forget to do something”?

Yes, with different patterns:

Forget something: gleyma + dative (e.g., Ég gleymdi símanum = “I forgot the phone.”)
Forget to do something: gleyma að + infinitive (e.g., Ég gleymdi að hringja = “I forgot to call.”)

Could I use “hafa” instead of “vera búinn að” (e.g., “Ég hafði gleymt töskunni”)?

Yes. Both are correct:

Ég hafði gleymt töskunni = past perfect with hafa + supine (neutral/standard).
Ég var búin(n) að gleyma töskunni = very common in speech; emphasizes resulting state (“was done having forgotten”). They usually mean the same thing; style and emphasis differ slightly.

Why not “Ég var næstum búna …”?

Predicate adjectives agree with the subject in the nominative. For a female speaker the nominative form is búin, not búna (which is accusative feminine). So:

Correct: Ég var næstum búin …
Incorrect: ✗Ég var næstum búna …

Are there other natural ways to say “almost” here?

Yes:

næstum and næstum því are both common: Ég var næstum (því) búin(n) að gleyma …
You can also say: Ég var við það að gleyma töskunni (“I was on the verge of forgetting the bag”), which puts extra stress on being right on the brink.