Conditional for Past Probability

Usually, the conditional describes what "would" happen. "I would go if I had money." But here, the function changes. We use the same verb form to look backward. It expresses an approximation. It expresses a doubt about a past fact. If someone asks, "What time did he arrive?" and you aren't sure, you use this. You are saying, "It was probably around..." It is like adding a "maybe" without saying the word talvez. It is a built-in uncertainty filter. Even native speakers use this to avoid being wrong. It is your best friend for making educated guesses.

1. 1Creating this is actually quite simple. You do not need to chop off verb endings. You just add to the whole verb.
2. 2Take the infinitive of the verb (like falar, comer, or ir).
3. 3Keep the r at the end.
4. 4Add the conditional endings: -ia, -ias, -ia, -íamos, -íeis, -iam.
5. 5Apply this to your past speculation.
6. 6For example, with ter (to have):
7. 7Eu teria (I must have had)
8. 8Você teria (You must have had)
9. 9Nós teríamos (We must have had)
10. 10Eles teriam (They must have had)
11. 11It is one of the most regular patterns in Portuguese. Even the irregular verbs like fazer (faria), dizer (diria), and trazer (traria) follow a predictable path. It is like a grammar cheat code.

Use this when you are guessing about the past.

• Speculating about age: Ela teria uns 20 anos na época. (She must have been about 20 at the time.)
• Guessing the time: Seriam seis da tarde quando o trem partiu. (It must have been 6 PM when the train left.)
• Expressing surprise or wonder: Quem seria aquele homem no bar? (Who could that man in the bar have been?)
• Estimating quantities: O concerto teria umas mil pessoas. (The concert probably had about a thousand people.)
• Job Interviews: "How many people were in your last team?" "Seriam uns dez." (It was probably about ten.)

It is perfect for when your memory is a bit foggy. Like trying to remember where you left your keys yesterday.

Do not use this if you are certain. If you know for a fact it was 5:00, use the Pretérito Imperfeito. Say Eram cinco horas. Using the conditional makes you sound unsure. Do not use it for future plans. That is a different context. Also, avoid it for simple "if/then" statements where no probability is involved. It is a tool for speculation, not for basic facts. Think of it like a "Caution" sign. If there is no doubt, take the sign down.

Many people use the Pretérito Imperfeito when they should use the conditional. They say Ele tinha 20 anos when they mean "He was probably 20." This sounds too factual. Another mistake is forgetting the accent on the í. Teríamos needs that accent. Without it, the rhythm is off. Don't mix it up with the future tense. Terá is about the future. Teria is about the past guess. Yes, even native speakers mess this up sometimes. Just keep your timeline straight. It is like a grammar traffic light. Green is for facts, yellow is for the conditional.

Compare Era vs Seria.

• Era meia-noite. (It was midnight. Fact.)
• Seria meia-noite. (It must have been midnight. Guess.)

Compare Tinha vs Teria.

• Ele tinha muito dinheiro. (He had a lot of money. You saw his bank account.)
• Ele teria muito dinheiro. (He probably had a lot of money. He drove a fancy car.)

One is a photograph; the other is a painting. One shows exactly what was. The other shows what might have been.