What does »'ne« mean?

Question

I read:

Ich warte schon 'ne Ewigkeit.

I suspect it means I have been waiting for whole eternity, or something like this. But I do not understand what 'ne means.

Answer 1

" 'ne" is the abbreviation for "eine". The apostroph omits the syllable "ei-". Note that this is a more colloquial writing and should not be used in a formal context.

EDIT:
As asked in the comments by the OP and answered by Eller, JohnDizzle, guidot and AnoE:

This construction does not work for definite articles.

However it works with other indefinite articles:

• 'n = ein
• 'nen = einen
• 'ner = einer
• 'nem = einem

But it works not for "eines" as " 'nes" is not used.

Answer 2

In regions, where Bavarian dialects are spoken (Bavaria and Austria), you might more often hear in similar settings:

Ich wart' schon a Ewigkeit.

Both, »a« and »’ne« are colloquial abbreviations for »eine«, but »’ne« is more common in middle and northern parts of Germany, while »a« has it's home in the south.

(Note, that there is also another minor change: The trailing e of warte is omitted in the south.)

Also the word »ein« can be shortened:

Standard German: »Gib mir bitte ein Glas Wasser.« (Please give me a glass of water.)
Colloquial, northern version: »Gib mir bitte ’n Glas Wasser.«
Colloquial, southern version: »Gib mir bitte a Glas Wasser.«

»einen«:

Standard German: »Du hast da einen Fleck.« (You have a stain there.)
Colloquial, northern version: »Du hast da ’nen Fleck.«
Colloquial, southern version: »Du hast da an Fleck.«

»einem«:

Standard German: »Er hat ihn mit einem Seil angebunden.« (He tied it with a rope.)
Colloquial, northern version: »Er hat ihn mit ’nem Seil angebunden.«
Colloquial, southern version: »Er hat ihn mit an Seil angebunden.«

(Note, that »einem« doesn't turn to »am« in the south, but also to »an«. Dative and accusative case often are the same in the southern colloquial speech.)

»einer«:

Standard German: »Iss den Reis mit einer Gabel!« (Eat the rice with a fork!)
Colloquial, northern version: »Iss den Reis mit ’ner Gabel!«
Colloquial, southern version: »Iss den Reis mit ana Gabel!«

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This doesn't work with definite articles (der, die, das, des, dem, den), and it also doesn't work with the male and neuter genitive indefinite article eines (»Das Kind eines Lehrers« doesn't turn into »Das Kind ’nes Lehrers« in the north, and in the south the genitive is even displaced with dative very often: »Das Kind vom Lehrer«)

Note, that all those abbreviations are not part of standard German. They are part of colloquial speech or even of regional dialects. As long, as you are not able to speak German without any foreign accent, nobody expects you to actively use such non-standard forms.

But when you talk with native speakers, you might hear such forms, and then you can remember what it means.

It's rather rare to finde one of those colloquial non-standard forms in written texts. If so, you might more likely find the northern versions, because they are closer to the standard