Learn French: Je pense que la ruche est pleine et j'en récolte le miel épais. - I think that the beehive is full and I harvest its thick honey.

In French, when talking about parts, contents, or products of an inanimate object (like a beehive), we often use en combined with the definite article (le, la, les) instead of the possessive adjectives son, sa, or ses. So instead of saying je récolte son miel, we say j'en récolte le miel (literally: I harvest the honey of it).

Why is there a le before miel if en already acts as 'its'?

Because en actually replaces the phrase de la ruche (of the hive). The underlying sentence is je récolte le miel de la ruche. When you replace de la ruche with the pronoun en, the definite article le must stay with the noun, giving us j'en récolte le miel.

Wait, shouldn't penser que trigger the subjunctive for the verb être?

No, verbs of opinion like penser que and croire que take the indicative mood (here, est) when they are in the affirmative. They only trigger the subjunctive when they are negative (like je ne pense pas que) or inverted in a question, because that is when they express genuine doubt.

Does the adjective épais have an extra 's' because we are talking about a large quantity of honey?