Difference between 'stets' and 'immer'

Question

I've found the word stets in some statements and I've learned that it means always, just like immer.

What is the difference between stets and immer?

Answer 1

stets:

as you mentioned it means: "always", personally I would prefer "whenever"
wiktionary gives two different meanings:

1. zu jeder Zeit, immer
2. bei jedem Anlass, jedes Mal, immer wieder

thus we can conclude, "stets" is more than immer about the instance of action.

Er war stets bemüht [...]
~Every time the writer saw him, he strived to [...]

immer:

again: "always", personally I believe as @Hagen von Eitzen said, one should translate as "all the time"
wiktionary here gives different meanings:

1. zu jeder Zeit
2. in häufig wiederkehrenden Intervallen
3. immer wenn: jedesmal, wenn
4. immer + Komparativ: weist auf eine sich zeitlich ändernde Intensität der Steigerung hin

from this we can conclude, that immer is primarily about some "period of time"

Er war immer bemüht [...]
~All the time he was striving to [...]

Answer 2

"Stets" has the connotation of "steadily" or "constantly." "Immer" is most often used as the translation for "always." They are similar in meaning, but not exactly the same.

Answer 3

The normal word in spoken and written language is "immer". In written language you can find the variant "stets".

Frequent function words often have a variant to avoid repetition in written language. So in this case. If you use "stets" in spoken language it is a bit out of the normal.

Answer 4

For the sake of full disclosure, I am not a native speaker of German and I am, at best, only at the A2 level. However, word frequency and collocation fascinate me and I often find that they help me with word choice in a foreign language, so allow me to share with you what I have discovered about these two words. As a bonus, I'm even going to throw in "allezeit," because what led me to this thread was a Google query of "What's the difference between "stets," "immer," and "allezeit."

---

Frequency

First, let's start off with a Google Ngram:

Clearly, "immer" has always been the most frequently used (at least in books). And, if the methodology of entering book texts into Google's Ngram database has been consistent, it appears that, for a short while, "allezeit" was more commonly seen than "stets."

---

Context

Here are some book excerpts from each of the three words you see above:

immer

... immer vorwärts bis an die Pforte der Revolution ...
... this freedom always steps forward to the gate of the revolution ...
—Dürfen die Fürsten Deutschlands bei dem immer fühlbarer ... - Page 55 by Lorenz Wolf (1821)

... immer kürzeren Zeiträumen ...
... ever shorter periods of time ...
—Liebenswert bist du immer: so schützen Sie Ihre seelische ... - Page 23 by Udo and Jakob Derbolowsky (2001)

Sie hat mir immer alles erzählt und anvertraut.
She always told and entrusted me with everything.
—Immer Nachts: Jugendroman - Page 229 by Daniela Buschmann (2004)

stets

... stets auf Einheit gerichtet ...
... rule is ultimately always focused on unity ...
—Der Führer - Page 44 by Walter Leisner (1983)

... mit Spannung erwarteten Ferien waren stets von besonderer Bedeutung, ...
... the eagerly awaited holidays were always of particular importance ...
—Spagat - Page 280 by Robert Becker (2003)

... stets kooperativen und hilfsbereiten Art ...
... always cooperative and helpful manner ...
—Systematische Mitarbeiterbeurteilungen und ... - Page 207 by Robert Müller (2005)

allezeit

I won't add quite as many book excerpts for "allezeit," because it became very clear to me that many of the books that contained this word were old (early 19th and sometimes 18th century) and many times were found in some type of religious text. I'll provide just a couple of examples so that you get the idea:

Ich will den Herrn loben allezeit ...
I want to praise the Lord always ...
—Christliches hausbuch: welches morgen- und abendandachten ... Page 628 by Magnus Friedrich Roos (1834)

... allezeit in messigkeit leben ...
... always live in moderation ...
—Die evangelischen Kirchenordnungen des XVI. Jahrhunderts: ... Page 937 by Emil Sehling (1957)

Oddly enough, the only other trend I noticed was that if the word "allezeit" wasn't found in a religious text, it was found in a scientific text (and was often related to nature of some sort (e.g., soil, rain, weather). Again, I'll just provide a couple of examples:

Das Regens wasser nämlich muß allezeit zuerst bis auf eine gewisse Tiefe in die Erde eindringen ...
The rainwater must always first penetrate the earth to a certain depth ...
—Vollständiger und faßlicher Unterricht in der Naturlehre mit ... Page 115 by Johann Michael Hube (1796)

Solche Schauer sind allezeit stark elektrisch , liefern aber nur dann einen oder einige wenige Blitze mit starkem Donner , wenn ...
Such showers are always strongly electric, but only deliver one or a few lightning bolts with strong thunder if ...
—Physikalisches wörterbuch - Volume 5, Part 1 - Page 70 by Johann Samuel Traugott Gehler (1829)

Very infrequently, did I find examples outside of this, but here is just one example:

... war er allezeit mit dem Andenken seines Tods beschäftiget ... ... he was at all times occupied with the memory of his death ...
—Kurze Lebensbeschreibung der Heiligen Gottes: mit den ... Page 204 by Hermann Goldhagen (1803)

Even so, note the title of this book (Brief biography of the saints of God).

---

Collocations

I used Digitales Wörterbuch der deutschen Sprache (DWDS) to examine the collocations for these words.

Though many have said that these words (well, at least "immer" and "stets") are interchangeable (and I don't doubt that), it does appear that the words more commonly found with "immer" aren't the same ones found for "stets" or for "allezeit." See for yourself with the collocations I found using Digitales Wörterbuch der deutschen Sprache (DWDS):

The DWDS page for each of these also has a link that allows you to see these collocations in table format, which also contains more numeric detail. For a larger view of the image above, using Chrome, right click and then click on "Open image in new tab."

So, as you can see, "präsent" has a strong correlation with "stets," but I should add that immer präsent is much more common than stets präsent. Other than that, I don't notice any tendencies that really stand out. The word "stet" does strike me as more often used with descriptions of positive connotation (e.g., friendly, loyal, faithful, smiling), but with each of these, you'll find that "immer" is more often paired with them:

The difference is even greater with those words most commonly paired with "immer":

Whenever I take a look at the collocations for words in another language, I usually take the time to see what they are in English (my native language). They aren't always the same. For example, some of the most common collocations I found for "always" were "always ready," "always happy," and "always welcome" (source: linguatools). Here's how their translations compare in German:

I almost decided to skip this for this answer since it was already so long, but I'm glad I didn't. Otherwise, I wouldn't have known that "all(e)zeit bereit" was more common than "stets bereit" and that "stets" was more commonly paired with "willkommen" than either "immer" or "all(e)zeit."

---

Note: When I first started answering this question, I was unaware that the word "allezeit" has "allzeit" as a variant. I avoided attempting to answer the differences between these two variants because 1) it didn't seem to be easily found and 2) it seems as if this would be best discussed or elaborated upon in a separate thread. For the record, other than frequency, I didn't notice any difference in usage, but there were quite a few more collocations found for "allzeit," (odd since it has a lower frequency than "allezeit" on the Google Ngram). Regardless, I went back and added those to the Google Ngram and cloud images, but did not elaborate on it much further.