undersöka means "to investigate, examine, look into, research." It is the all-purpose verb for systematically finding something out — whether a doctor checking a patient, a detective looking into a case, or a researcher studying a question. Structurally it is under- ("under") + söka ("seek, search"), and it inherits söka's conjugation cell for cell: a Group 2 -te verb, undersöka – undersöker – undersökte – undersökt. The literal "search under (the surface)" image captures the sense nicely — you look beneath the obvious to find out what's really going on.
Principal parts
| Infinitive | Present | Preteritum (past) | Supine | Imperative | Group |
|---|---|---|---|---|---|
| undersöka | undersöker | undersökte | undersökt | undersök | Group 2 (-te), prefixed söka |
The key detail is the -te endings. Because söka's stem ends in a voiceless k (sök-), the past takes -te (not -de): undersökte, and the supine takes -t: undersökt. This is the standard rule for Group 2 verbs whose stem ends in a voiceless consonant. The present adds -er normally (undersöker, unlike the -föra verbs), and the imperative is the bare stem undersök. The past is never undersökade — that would be the wrong group entirely.
Polisen undersöker fortfarande olyckan.
The police are still investigating the accident. Present undersöker.
Läkaren undersökte mig noggrant.
The doctor examined me thoroughly. Past undersökte — Group 2 -te.
Vi har undersökt alla möjligheter.
We've looked into every possibility. Perfect har undersökt.
Use 1: a doctor examining a patient
In medical contexts undersöka is the standard verb for a physical examination — a doctor, nurse or vet checking a patient or body part.
Kan du undersöka mitt knä? Det gör ont när jag böjer det.
Can you examine my knee? It hurts when I bend it.
Veterinären undersökte hunden och hittade inget allvarligt.
The vet examined the dog and found nothing serious.
Use 2: researchers and investigators looking into a question
The same verb covers academic research, journalistic digging and official inquiries — anywhere you systematically study a question, a claim or a case.
Forskarna undersöker hur sömn påverkar minnet.
The researchers are investigating how sleep affects memory.
Vi måste undersöka saken närmare innan vi bestämmer oss.
We have to look into the matter more closely before we decide.
En oberoende kommission ska undersöka vad som hände.
An independent commission is to investigate what happened.
Use 3: the noun en undersökning
The action noun is en undersökning, and its breadth is worth memorising: the same word covers a medical examination, a scientific study, and an opinion survey. Context tells you which.
Jag har en undersökning hos tandläkaren imorgon.
I have a check-up at the dentist tomorrow. Medical sense.
En ny undersökning visar att de flesta är nöjda.
A new survey shows that most people are satisfied. Poll/study sense.
Resultaten av undersökningen publicerades i fjol.
The results of the study were published last year.
Common Mistakes
❌ Läkaren undersökade mig.
Incorrect — undersöka is a Group 2 verb (it inherits söka), not Group 1. The past is undersökte, never -ade.
✅ Läkaren undersökte mig.
The doctor examined me.
❌ Vi undersökde frågan i veckan.
Wrong past ending — söka's stem ends in voiceless k, so it takes -te, not -de: undersökte.
✅ Vi undersökte frågan i veckan.
We looked into the question this week.
❌ De har undersökat saken.
Wrong supine — for a -te verb the supine ends in -t on the stem: undersökt, not undersökat.
✅ De har undersökt saken.
They've looked into the matter.
❌ Vi gjorde en undersökelse om vanorna.
Wrong noun — there's no *undersökelse. The action noun is en undersökning.
✅ Vi gjorde en undersökning om vanorna.
We carried out a survey on the habits.
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Start learning Swedish→Related Topics
- Using the Verb ReferenceA2 — How to read the single-verb reference cards and the principal-parts citation system that underpins them. Every Swedish verb is cited as a short chain — infinitive – present – preteritum – supine – (past participle) — because every other form is derivable from those parts. This page decodes one weak verb (tala – talar – talade – talat) and one strong verb (skriva – skriver – skrev – skrivit – skriven), explains the conjugation-group labels (1/2/3/4), and gives a key to everything on a card.
- The Four Conjugation GroupsA2 — Swedish verbs sort into four conjugation classes, identified not by the present tense but by the PAST (preteritum) and supine: Group 1 (talar/talade/talat), Group 2 (ringer/ringde/ringt, köper/köpte/köpt), Group 3 (bor/bodde/bott), and Group 4, the strong verbs (skriver/skrev/skrivit) that change their vowel. Group 1 is so dominant and regular that every new and borrowed verb joins it — so treat it as the default and memorise only the closed list of strong verbs.
- Prefixed (Inseparable) Verbs (förstå, bestämma)B2 — Swedish has two opposite verb-building systems: native particles that are STRESSED and split off (stå ut), and borrowed prefixes be-, för-, an-, und-, er- that are UNSTRESSED, glued on, and never separate (förstå, bestämma). Stress placement alone tells you which system a verb belongs to.