When traveling abroad, are you "oversea" or "overseas"?

I live in Singapore and I will be travelling to Jakarta.

Should I say "I will be oversea next week." or "I will be overseas next week."?

Looking at Google Maps, it looks like there are two seas between Singapore and Jakarta.

Is there any instance where I should use "oversea"?

Solution 1:

You should use overseas: both oversea and overseas literally mean across a sea, but overseas is much more common for the abstract meaning of abroad. So if you're talking about literal travel across a sea, use oversea:

I work in oversea shipping.

While if you mean generally abroad, use overseas:

Is there an extra charge for overseas shipping?
I will be overseas next week.

Edit: Just to clarify, as @kiamlaluno points out, these words make no distinction about the number of seas that you cross. Seas in this sense is not literally the plural of sea, but rather the abstract notion of the waters of the sea that you cross when you go oversea, as opposed to the lands that you cross when you go overland.

Solution 2:

I would go with:

I will be overseas next week.

Overseas, an adverb, means to go beyond the seas. Even with an 's' at the end, I think it still functions as a singular (confirmation anyone?). The number of seas doesn't make a difference, and one sea doesn't mean you have to use oversea. See this link for definitions:

http://mw1.merriam-webster.com/dictionary/overseas

However, Merriam Webster also lists oversea, mainly British usage, as having the same meaning as overseas. Acoording to them oversea was used first, in the 12th century, compared to overseas, in 1533. Nowadays, without offence to the Brits, you hardly hear oversea used.

The nearest synonym to overseas is abroad.

I will be abroad next week.

An occasion when you might use over sea (note separation):

They travelled over sea and land.

which, to my ear, sounds better than:

They travelled over seas and lands.

The other issue is whether overseas would apply if you were travelling to another country without crossing any sea or seas.

By the way, don't confuse overseas with oversee, which means to supervise or to watch over.

Solution 3:

Maybe it's just me, but that expression sounds very pompous when applied to relatively short distances, no matter how many seas are in between.

When I lived in UK, I never heard the term oversea or overseas applied to continental Europe.

Go simple and you won't go wrong, just say "I'll be in Jakarta next week".