Portuguese has two distinct simple past tenses where English uses one, and the difference isn't optional style, it changes what a sentence actually claims. The pretérito perfeito (which most learners just call the preterite) marks a single completed action: something happened, once, and the sentence is reporting that event. The pretérito imperfeito (the imperfect) marks something ongoing, habitual, or still in progress at the time being described. English collapses both into "announced," "was studying," or "used to say" depending on context, but Portuguese marks the distinction directly in the verb ending, every time, and real news writing leans on that distinction constantly to separate the main event from its background.
The practical difference, in one pair of sentences
"O governo anunciou uma reforma fiscal" (the government announced a fiscal reform) uses the preterite, anunciou: this happened, as a single completed event, this is the news. "O governo estudava uma reforma fiscal há vários meses" (the government had been studying a fiscal reform for several months) uses the imperfect, estudava: this was ongoing, ambient context rather than the reportable event itself. News articles routinely combine both in one sentence: "O primeiro-ministro anunciou esta terça-feira que o governo estudava a reforma há meses," announced (preterite, the news) that the government had been studying it for months (imperfect, the background). Recognizing which tense you're reading tells you, instantly, whether a verb is the headline event or the context around it.
How to recognize the forms
Regular -ar verbs (like anunciar, estudar): preterite endings are -ei, -aste, -ou, -ámos, -aram (anunciou, anunciaram); imperfect endings are -ava, -avas, -ava, -ávamos, -avam (estudava, estudavam). The imperfect's -ava/-avam pattern is distinctive and, once recognized, easy to spot on sight across almost any -ar verb.
Regular -er and -ir verbs (like dizer-type patterns, though dizer itself is irregular; a regular example is vender): preterite endings are -i, -este, -eu, -emos, -eram (vendeu, venderam); imperfect endings are -ia, -ias, -ia, -íamos, -iam (vendia, vendiam). The -ia/-iam imperfect ending is the equivalent recognizable signal for this verb group.
A handful of very common verbs are irregular in both tenses and worth knowing directly rather than deriving from the pattern: ser and ir share the same preterite forms (foi can mean either "was" or "went," disambiguated by context), while their imperfects diverge (era for ser, ia for ir). Ter's preterite is teve; its imperfect is tinha, which shows up constantly in background description ("o país tinha uma economia frágil," the country had a fragile economy at the time).
Why this matters more in news than in conversation
Spoken Portuguese uses both tenses too, but a news article's structure depends on the contrast more heavily, because news writing is built around exactly this distinction: report the event (preterite), then supply the context that explains or surrounds it (imperfect). A paragraph describing a court ruling might use the preterite for the ruling itself and the imperfect for the situation the court was addressing, the ongoing dispute, the policy that had been in effect, the practice that was occurring. A reader who treats every past-tense verb as interchangeable misses that structural signal entirely and has to reconstruct which parts of the paragraph are the actual news from context alone, rather than reading it directly off the verb forms where the writer already marked it.
A longer worked example, with both tenses doing real work
Take a paragraph closer to what actually runs in a Portuguese newspaper: "A câmara municipal aprovou ontem o novo plano de mobilidade. A proposta estava em discussão há mais de um ano e enfrentava resistência de vários moradores que temiam o aumento do trânsito na zona histórica." The first sentence, aprovou, is the preterite: the council approved the plan, yesterday, a single completed event, this is the headline fact. The second sentence shifts entirely into the imperfect: estava (was under discussion), enfrentava (was facing resistance), temiam (feared). None of that is new news; it's the yearlong backdrop the reporter is filling in so the approval makes sense. A reader tracking only "what happened" can, after the first sentence, treat the rest of the paragraph as context rather than trying to parse three more events, because the imperfect is telling you directly that nothing new is being reported there.
An edge case worth knowing: costumava + infinitive
Portuguese has a second, periphrastic way to mark a habitual past that doesn't rely on the imperfect ending alone: costumava plus an infinitive, as in "ele costumava ler o jornal todas as manhãs" (he used to read the newspaper every morning). This shows up often in feature writing and profile pieces, less in hard news, and it's easy to miss if you're only watching for -ava/-ia endings, because costumava itself is the imperfect form doing the marking while the actual habitual verb, ler, stays in the infinitive and gives no tense signal of its own. Recognizing costumava as a habitual-past marker, not just a random verb meaning "to be accustomed to," closes that gap.
A fast reading habit
Once you notice a verb in -ava, -avam, -ia, or -iam, treat it as background or ongoing rather than the main event, and keep reading for the preterite verb nearby that's likely doing the actual reporting. This isn't a rule to apply consciously to every sentence forever; it becomes close to automatic within a few weeks of reading real Portuguese news paragraphs where the pattern repeats constantly, event in preterite, context in imperfect, article after article.
It's worth separating this from a mistake app courses sometimes leave unaddressed: the imperfect isn't a weaker or less complete version of the preterite, and reaching for it isn't a grammar error to avoid. Both tenses are equally correct, doing genuinely different jobs. A sentence that uses the preterite where the imperfect belongs, or the reverse, doesn't just sound slightly off, it changes what actually happened, which is exactly why real writers use the contrast so deliberately rather than picking one tense and staying with it.