Yes, and also write. ”Sade” is only found in writing, and you may choose between ”sa” or ”sade” when writing, the latter being the older form. Same goes for ”lade” (lay), however, ”la” is still considered a bit colloquial when writing, whereas ”sa” is not.
In general the -de-ending of past tense verbs is usually omitted in speech.
My girlfriend who is Swedish said that "sa(de)" is the only exception among verbs that can be shorten, both in writing and speaking, but all other verbs is recommended to use them in full form, also in writing and speaking. The same goes with "hade". She said that I shouldn't say "ha" and that people just don't talk like that.
Ha instead of hade is completely wrong. Nobody would ever say that or it wouldn’t even occur to someone to say that, because ha is the infinitive form.
To possibly elaborate more on what I said above and what your girlfriend said. Dropping -de in -ade is common everywhere. The verbs säga - sade and lägga - lade are a bit different because they’re irregular verbs and the a in the past tense is a long a as compared to the normal -ade ending where it is short.
The past tense of säga can be either sade or sa. Originally, sa was considered more colloquial but today it is the preferred way of writing säga in the past tense and sade can be considered a bit formal or old-fashioned, depending on the context.
The verb lägga is a bit behind säga and they’re not 100% comparable. Lägga is maybe where säga was 50 years ago or so. For lägga, the past tense is normally written lade and the spelling la is considered quite colloquial.
If you were reading a normal novel or a news article in Sweden you would probably mostly see sa and some sade here and there, depending on the author’s preference, but you would most likely primarily see lade and not so many la, it would be expected to be found maybe in dialogues or informal articles.
Please note that people sometimes pronounce the full -ade ending in regular verbs like pratade, but it is much more uncommon to pronounce the full ending in sade/sa or lade/la, they, and especially sade, are 99% of the time pronounced as sa and la, that’s why they can also be written this way.
So if I understood correctly, any verb with -ade, like pratade, talade, sade, lade, regnade etc, they just drop 'de' so they become prata, tala, sa, la, regna?
Correct. However sa and la are a bit different because they have a long final vowel, and they are accepted in writing. The first one is completely accepted and the latter one is somewhat of a colloquial spelling. For the other verbs, it’s incorrect to leave out the -de in writing.
Question: (and maybe this is taught further along the tree) When an English speaker answers this question, they're likely to say, "No, I didn't" or "Yes, I did" with (hear what you said) being implied. In Swedish there's no actual word that translates into the "did", it's implied in the English translation because that's what would be grammatically correct. So my question is, how would a Swede answer this question (other than just "ja" or "nej") that equates to "No, I didn't" or "Yes, I did"? Is this possible, or would you just say "Ja, jag hörde" or "Nej, jag hörde inte"? Tack!