No difference in meaning...it's dialect/regional thing. "Mas" is used more in the south, whereas "allan" is more common in the north.

Ma's is an older spelling of mas. They mean exactly the same thing - "out". You'll see both spellings used in the wild. I'm not sure which one Duolingo prefers.

The reason for the version with the apostrophe is that the word comes from i maes, literally "to (the) field/open country" i.e. "to the outside". In the south, ae in a single syllable word is often pronounced as a long a colloquially and this is how everyone pronounces it in this word now, hence the spellings ma's/mas.

The most common word for "field" today is cae but maes is still used sometimes. It refers especially to a patch of ground for a specific purpose e.g.

maes glo "coalfield"

maes y gad "battlefield"

maes chwarae "playground"

maes parcio "car park"

maes awyr "airport"

It's also used for more abstract "fields" e.g. a field of study or a field in a spreadsheet.

Allan is the standard word, so you'll see it written in public places in the south too, such as road markings and signs like Ffordd allan "way out".

There are many different words used between the north and south but one is usually the preferred "standard".

i.e.

Here are a few others, with the standard word in italics

allan (N) mas (S) out

bwrdd (N) bord (S) table

dallt (N) deall (S) understand

efo (N) gyda (S) with

Two different tenses in both Welsh and English:

• Es i - I went (simple past, or preterite) (covered later in this course)
• Dw i wedi mynd - I have gone (present perfect)