I would say that they are not always interchangeable because they can be used in two ways:
- nous serons au moins 10 à la fête (we will be at least 10 at the party) = at minimum
- nous serons 10 à la fête, du moins en ce qui concerne les adultes (we will be 10 at the party, at least when it comes to adults) = restriction/slight correction of what was just said
"en ce qui concerne" is a fixed phrase (with regard to, regarding, about, when it comes to...).
"concerner" is a verb that you can use separately.
- cet article concerne un cheval = this aerticle is about a horse
"en ce qui" might be used in a suitable context:
- Ce chapitre stipule l'obligation d'information d'une entité en ce qui a trait à ses objectifs, politiques et procédés de gestion [...] = This section establishes an entity's disclosure requirements regarding its objectives, policies and processes for managing [...]
I came across this excellent distinction today: « Il a au moins 100 euros. » vs « Il a du moins 100 euros. » In the first instance he has no fewer than 100 euros, probably more. In the second he has exactly 100 hundred euros and that's better than nothing. "He has at least 100 euros." vs "At least he has 100 euros."
This distinction is interesting but I am not sure you will have lots of occasions to use it.
"Il a du moins 100€" is something even I do not understand.
"Du moins a-t-il 100€" is slightly better (at least/however/though/yet, he has 100€) but it is not crystal clear.
To mean the latter, it is way easier to use "Au moins, il a 100€" (meaning: that's a good start); vs "il a au moins 100€" (that is the minimum he may have, may be he has more).
In this sentence, the difference is not crystal clear.
Here are other examples:
tu dois avoir au moins 18 ans pour conduire une voiture (= 18 years of age is a minimum)
tu dois avoir 18 ans pour conduire une voiture, du moins en France (= restriction of the statement to France)
It seems strange to use croire without some kind of object, either "il le croyait" or "il croyait que oui" (or maybe "il y croyait"? "il lui croyait"?). In English "He believed!" by itself could have the narrow meaning of "He became a believer in God!" Does "Il croyait!" without an object have the same meaning in French?
In French, the past imperfect is used for repeated/habitual actions as well as the slightly more fuzzy area of thoughts and feelings when a specific time is not given. For example, you would say "Il faisait bien" when referring to the weather, but you also say "À minuit hier soir, il a neigé" because that is a specific time. In this question, we are not given a specific time for when he believed, so it is "Il croyait" instead of "Il a cru"
Wow that is nuanced, but when I try those stative verbs in a continuous manner, the sentences don't sound right. "I was hearing the concert yesterday." Nope. "I was listening to the concert yesterday." Yep. ... but this begs the question, how is it we should know that a verb is stative in French? Are these categories universal or arbitrary? My guess is the latter. One doesn't see the categorization given in dictionary entries.
Question related to https://www.duolingo.com/skill/fr/Adjectives-3,<pre>
Paul est le meilleur. — Paul is the best. Ses filles sont les meilleures. — Her daughters are the best.</pre>
Here "meilleur" and "meilleures" are adjectives or adverbs. To me they seem adverbs modifying the verbs "est" and "sont".
At least has two meanings in English. The french are more specific with au moins/du moins.
1] At least = not less than; at the minimum. Eg, clean the windows at least once a week.. "Au moins" in French carries this import.
2] At least = if nothing else; in any case. Eg, the options aren't complete, but at least they're a start. "Du moins" in French carries this second import. It used to qualify or add a positive spin about a generally negative situation.
As we know, in English, if "Think" means "to have an idea or opinion" it cannot be used in continuous form but if it means "consider" it can be. With that in mind, can we translate "il croyait" to both "I was thinking" and "I thought" here in this sentence, can't we? If not, which one is the exact meaning of this verb here?