The past tense of the verb "to be" is one of the very first building blocks you need in Serbian, and the good news is that it is completely regular and entirely learnable in a single session. Once you have it, you can describe where you were, how you felt, and who was with you - all the things that make real conversation possible.
Today we practise this by watching a short video and then responding to prompts based on photos. It is a wonderful way to make the forms feel real rather than abstract. Let us take it step by step.
How do you form the past tense of "to be"?
The past tense of biti (to be) is formed by combining the present tense of biti as an auxiliary (sam, si, je, smo, ste, su) with the past participle, which agrees in gender and number with the subject. The masculine singular form is bio, the feminine singular is bila, the neuter singular is bilo, and the plural form is bili (masculine or mixed) or bile (feminine plural).
So for a man: ja sam bio (I was). For a woman: ja sam bila (I was). This gender agreement is a central feature of all Serbian past tenses - not just "to be" - so getting comfortable with it here will help you across the board.
The forms
The table below gives you every form you need. Study the masculine and feminine columns side by side - the only difference is the ending of the participle.
| Person | Masculine | Feminine | Meaning |
|---|---|---|---|
| 1st sg. | ja sam bio | ja sam bila | I was |
| 2nd sg. | ti si bio | ti si bila | you were |
| 3rd sg. | on je bio | ona je bila | he/she was |
| 3rd sg. neut. | ono je bilo | it was | |
| 1st pl. | mi smo bili | mi smo bile | we were |
| 2nd pl. | vi ste bili | vi ste bile | you (pl.) were |
| 3rd pl. | oni su bili | one su bile | they were |
Hear it
Watch the video below and listen carefully to how these forms sound in natural speech. Pay attention to how the auxiliary (sam, si, je...) blends smoothly with the participle - in spoken Serbian they run together almost as one unit.
The task
Watch the video and, as you go through it, write down the questions and answers based on the photos and prompts that appear on screen. You can also record yourself speaking the answers aloud - hearing your own voice is an excellent way to check your pronunciation and build confidence.
For each photo prompt, ask yourself: who is in the picture, where were they, and how might they have felt? Then form the correct past tense of "to be" - remembering to match the gender and number of the participle to the subject. If you are working through this with a study partner, take turns asking the questions and giving the answers.
More Serbian examples
Here are some full sentences to anchor the forms in your memory. Read them, translate them mentally, and then try covering the English and checking yourself.
Bio sam kod kuce.
I was at home.
Ona je bila umorna.
She was tired.
Gde si bio juce?
Where were you yesterday?
Mi smo bili u Beogradu prošlog vikenda.
We were in Belgrade last weekend.
Da li si bila na koncertu?
Were you at the concert?
Oni su bili veoma sreni.
They were very happy.
Vreme je bilo lepo.
The weather was nice.
Gde ste bili sino?
Where were you (plural) last night?
Bila sam na poslu ceo dan.
I was at work all day.
On je bio nastavnik u osnovnoj školi.
He was a teacher in primary school.
Frequently asked questions
Can I drop the subject pronoun in the past tense?
Yes - and in spoken Serbian you very often do. Since the auxiliary already encodes the person (sam = I, si = you, smo = we), saying Bio sam umoran (I was tired) is perfectly natural without ja. The pronoun is typically added only for emphasis or contrast: Ja sam bio umoran, ali ti nisi (I was tired, but you weren't).
What happens in questions?
To form a yes/no question, add da li at the start or add li after the auxiliary: Da li si bio kod kuce? or Jesi li bio kod kuce? Both mean "Were you at home?" Note that in questions the long form jesi replaces the short form si when li follows directly. This is a small but important detail.
What about negative sentences?
Negate by adding ni- to the auxiliary: nisam bio (I was not), nisi bio (you were not), nije bio (he was not), nismo bili (we were not), niste bili (you were not), nisu bili (they were not). The negative forms are single words - there is no separate "not".
Does the same gender-agreement rule apply to all Serbian past tenses?
Yes - every verb in the Serbian past tense uses the same past participle system, and the participle always agrees in gender and number with the subject. This is one rule worth internalising early because it applies throughout the language.
Is the past of "to be" used as an auxiliary for other verbs too?
Exactly - the present tense of biti (sam, si, je, smo, ste, su) is the standard auxiliary for forming the past tense of every verb in Serbian. So once you are comfortable with ja sam bio, you are also well on your way to ja sam ucio (I was learning / I learnt) and ja sam išao (I was going / I went).
The past tense of "to be" is a small piece of grammar with an enormous reach. Every Serbian past tense sentence you will ever produce depends on this foundation, so the time you invest here today pays dividends across everything you learn next. You are doing wonderfully - keep going!
- Marina Petrovic