Höst is the Swedish word for 'autumn' – not to be confused with hosta (cough). Hear how to say it in the clip below:
As for how to use it, it depends on which autumn you are referring to.
I höst means 'this autumn', which you say if you are talking about the upcoming autumn, or if the season has already begun. You use it with the future or present tense. For example: jag ska gifta mig i höst = I will get married this autumn.
I höstas means 'last autumn', and you use it to talk about the previous autumn, using the past tense. In this context you can also say förra hösten (last autumn). For example: Jag gifte mig i höstas = I got married last autumn.
På hösten means 'in the autumn' and you use it to talk about autumn in general, usually with the present tense. For example: Jag vill gifta mig på hösten = I want to get married in the autumn (in general, no specific autumn).
To talk about the autumn of a specific year, past or future, you can say hösten + year, for example jag gifte mig hösten 1993 = I got married in the autumn of 1993.
In Sweden, the autumn season has a strict meteorological definition.
Höst only arrives once the average daytime temperature has stayed below an average of 10C for five consecutive days. When that threshold is reached, the first day of the five-day period is considered the start of autumn. Autumn then becomes winter when the average temperature is below an average of 0C for five consecutive days. That means höst arrives and lasts for very different times depending on where you are in the country.
Höst originally meant 'harvest', with both the Swedish and English words related to the Old Norse word haust. Haust originally referred to gathering, but became used as the general term for the season in which farmers gathered their crops.
In the UK, as populations moved away from rural living, haust was overtaken by 'autumn' from the Latin term autumnus in general speech, and from the 1500s onwards 'harvest' took on a narrower, specifically agricultural meaning. But further north, rural farming societies lasted much longer and they and their languages were less influenced by Latin. So Sweden kept the word höst, which is related to German der Herbst and Norwegian haust. Today, the Swedish word for 'harvest' is skörd.
And like in English, you can talk about höst figuratively to talk about a late stage in a process, for example på livets höst (in the autumn of life), a metaphorical way to refer to older age.
Det blir en tidig höst i år
Autumn is coming early this year
Jag kom till Sverige hösten 2002
I came to Sweden in the autumn of 2002