"The bear eats an apple."
Translation:L'ours mange une pomme.
I don't know what you mean by "attribution".
anyhow, l'ours is le + ours (masculine) but le is elided (drop the e and replace it by an apostrophe), to ease translation whenever the noun starts with a vowel or a non-aspired H:
le chien - l'ours (masculine)
la chienne - l'ourse (feminine)
l'honneur (masc) - l'huile (fem)
It is one of many exceptions to the rule you will find. I.e., that's just the way it is. http://www.larousse.fr/dictionnaires-prononciation/francais/ours/003795
If the noun begins with a vowel (or a vowel sound), you must contract the definite article:
- l'homme (m) : contraction is required because homme starts with a vowel sound.
- l'araignée (f) : contraction is required because araignée starts with a vowel.
- la pomme (f) : no contraction (ever)
- le pain (m) : no contraction (ever)
If you keep posting stuff with translations like this it will give people the answers to things