Learn Hardcore Icelandic: Ég hef unnið í þessari verslun áður.

Hef unnið is the present perfect. It combines the auxiliary hef (1st person singular of hafa, “to have”) with the past participle unnið of vinna. It expresses an action that started in the past and has relevance to the present (“I have worked”).

Why do we use ég hef unnið instead of just ég unnið?

In Icelandic perfect tenses you always need the auxiliary hafa + past participle. Without hef, ég unnið would be ungrammatical. If you drop hafa and change the verb form, you get the simple past: ég vann (“I worked”).

Why is í þessari verslun in the dative case?

The preposition í, when indicating location (“in”), governs the dative case. Verslun is a feminine noun; its dative singular form stays verslun, and the demonstrative þessi must agree, becoming dative feminine þessari. Hence í þessari verslun.

What’s the difference between Ég hef unnið and Ég er búinn að vinna?

Both express the perfect aspect. Ég hef unnið uses hafa + past participle. Ég er búinn að vinna uses vera + adjective búinn + infinitive að vinna (literally “I am finished having worked”). The vera + búinn + að construction is very common in speech; hef unnið is more formal/literary.

What does áður mean, and why is it at the end?

Áður is an adverb meaning earlier or before. In Icelandic, such time-adverbs often follow the verb phrase or come at the end of the sentence for emphasis: Ég hef unnið í þessari verslun áður (“I have worked in this store before”).

Why is the past participle unnið and not something else?

Vinna is a strong (irregular) verb with the paradigm: present vinna, past vann, past participle unnið. Many strong verbs don’t follow a single rule, so you learn their participles individually.

How do I know verslun is feminine, and why does þessi change to þessari?

Dictionaries mark verslun as a feminine noun. Demonstratives like þessi must agree in gender, number, and case with the noun. For feminine singular dative, þessi becomes þessari, matching í þessari verslun.