Learn Russian: Заместитель уверен в этом решении. - The deputy is confident in this decision.

Nouns that end in -ие in their dictionary form (like решение, meaning "decision") are an exception to the standard rule. In the Prepositional case, they take an -и ending instead of an -е. So, решение becomes в решении.

Why is the short adjective уверен used here instead of the full word уверенный?

In Russian, short-form adjectives are often used as the main predicate of the sentence to show a state of being or a current feeling. When saying someone "is sure" or "is confident," you almost always use the short forms: уверен for a man, уверена for a woman, and уверены for plural.

What case follows the phrase уверен в?

It requires the Prepositional case. While the English translation is "confident in", it's also commonly used to mean "sure of". It is important to remember that уверен в always triggers the Prepositional case, which is why это and решение both change to their Prepositional forms: этом решении.

Is there a trick to remembering the word заместитель?