Hunden började halta igår.

Hunden is the definite singular form of hund.

• hund = dog
• en hund = a dog
• hunden = the dog

In Swedish, the definite article is usually added as an ending on the noun, instead of being a separate word like English the.

So:

• hund → hunden
• katt → katten
• bil → bilen

Because Swedish usually puts the at the end of the noun as a suffix.

So instead of saying something like the dog, Swedish normally says hund-en.

A separate word such as den is used in some other situations, for example:

• den stora hunden = the big dog
• den hunden = that dog / that particular dog

But in a simple phrase like the dog, hunden is enough by itself.

Började is the past tense of börja, which means to begin or to start.

Useful forms:

• börja = infinitive, to begin/start
• börjar = present tense, begins/starts
• började = past tense, began/started
• har börjat = has/have begun, started

So Hunden började halta igår is in the past because the starting happened yesterday.

After börja, Swedish commonly uses another verb in the infinitive:

• börja halta = start limping
• börja springa = start running
• börja äta = start eating

In English, you might say either:

• started limping
• started to limp

Swedish often just uses the infinitive directly here: började halta.

You may also sometimes see började att halta, but without att is very common and natural.

That is a very natural place for a time expression in Swedish.

The sentence structure here is:

• Hunden = subject
• började = finite verb
• halta = infinitive verb
• igår = time expression

So the pattern is basically:

subject + verb + infinitive + time

Putting igår at the end sounds neutral and normal.

Yes. You can also say:

Igår började hunden halta.

That is also correct and means the same thing.

But when something other than the subject comes first in a Swedish main clause, the finite verb must still stay in second position. That is why it becomes:

• Igår började hunden halta not
• Igår hunden började halta

This is an important Swedish word-order rule called V2 word order.

Yes. Halta can be used for both.

Examples:

• Mannen haltar. = The man is limping.
• Hästen haltar. = The horse is limping.
• Hunden började halta igår. = The dog started limping yesterday.

It can also be used figuratively sometimes, like saying that something is not working properly, but in this sentence the meaning is literal.

A rough guide:

• började sounds roughly like BUR-yah-deh, but with a Swedish ö sound
• igår sounds roughly like ee-GOR, where å is a long vowel somewhat like the vowel in more for many English speakers

A few important points:

• ö in började does not have an exact English equivalent. It is often approximated by something like the vowel in British bird, but with rounded lips.
• j in Swedish usually sounds like English y
• the stress in igår is on the second syllable: i-GÅR

These are only rough guides, but they can help at the beginning.

Yes, but it means something slightly different.

• Hunden började halta igår = The dog started limping yesterday.
• Hunden haltade igår = The dog was limping yesterday / limped yesterday.

The original sentence focuses on the beginning of the limping.
The version with haltade just tells you that the dog limped yesterday, without emphasizing when it started.