I received the following question on Tuesday:
“I have been working on my German and have a question – I can’t seem to find the answer. In the accusative, does sein and dein change to seinen and deinen? I know that ein, mein, ihr, unser all get an “-en” when in the accusative…”
First of all, if you don’t remember / know what possessive adjectives are, click here.
Response from German Learning Help:
In regard to singular nouns: Ja wohl! All the possessive adjectives get an -en in the Accusative case – but only if the noun that’s the direct object is masculine.
The following masculine examples are the ones that get the -en. There is no -en with the feminine and neuter nouns if they are singular.
Masculine Accusative Examples:
der
With definite article: Ich sehe den Mann. – I see the man.
With indefinite articles:
Ich sehe einen Mann. – I see a man / husband.
Ich sehe meinen Mann. – I see my man / husband.
Ich sehe deinen Mann. – I see your man / husband.
Ich sehe seinen Mann. – I see his man / husband.
Ich sehe ihren Mann. – I see her man / husband.
Ich sehe seinen Mann. – I see its man / husband. (Most unlikely example here).*
Ich sehe unseren Mann. – I see our man / husband.
Ich sehe eueren Mann. – I see y’all’s man / husband.
Ich sehe Ihren Mann. – I see your man / husband (formal).
Ich sehe ihren Mann. I see their man / husband.
* Note: Technically, the possessive adjectives could refer back to any noun of matching gender. A noun could have the gender der, die, or das. Correspondingly, “sein,” “ihr,” and “sein,” (the last of these referring back to a das word), could all mean “its” – referring back to any noun of those genders (not necessarily a person for sein and ihr).
The bold -en each time comes after the possessive adjective word. However, there is no -en with the feminine and the neuter if they are singular.
die
Feminine Accusative Examples
With the definite article: Ich sehe die Frau. – I see the woman.
With indefinite articles:
Ich sehe eine Frau. – I see a woman / wife.
Ich sehe meine Frau. – I see my woman / wife.
Ich sehe deine Frau. – I see your woman / wife.
Ich sehe seine Frau – I see his woman / wife.
Ich sehe ihre Frau. I see her woman / wife.
Ich sehe seine Frau. – I see its woman. (Most unlikely example here)*
Ich sehe unsere Frau. I see our woman / wife.
Ich sehe euere Frau. I see y’all’s woman / wife.
Ich sehe Ihre Frau. (I see your wife).
Ich sehe ihre Frau. (I see their woman / wife).
* Note: Technically, the possessive adjectives could refer back to any noun of matching gender.
das
With definite article: Ich sehe das Baby
With indefinite articles, all the words coming before the nouns are just the possessive adjectives themselves, with no -en or -e at the ending.
Ich sehe ein Baby. – I see a baby.
Ich sehe mein Baby. – I see my baby.
Ich sehe dein Baby. – I see your baby.
Ich sehe sein Baby. (I see his baby).
Ich sehe ihr Baby. I see her baby.
Ich sehe sein Baby. (I see its baby).*
Ich sehe unser Baby. (I see our baby).
Ich sehe euer Baby. (I see y’all’s baby).
Ich sehe Ihr Baby. (I see your baby). – formal
Ich sehe ihr Baby. (I see their baby).
* Note: Technically, the possessive adjectives could refer back to any noun of matching gender.
In summation for the singular in the accusative case, there is an -en on the end of the der words (masculine), but not for the die (feminine) and the das (neuter) words. In the accusative case you can think of it this way: der words (masculine) have an -en that sticks out. The feminine “die” words have that oh-so-feminine -e that looks so dainty. The neuter ones have no masculine -en sticking out, and no oh-so-dainty -e, just the bland ol’ possessive adjectives themselves.
You may be wondering about how it looks in the plural. Do you want me to go there? All of the above examples are examples with singular nouns.
Ich hoffe, das hilft.

Thanks for good stuff