Learn Italian: Il medico non sapeva che il mio smarrimento fosse così profondo. - The doctor didn't know that my bewilderment was so deep.

The phrase non sapeva che is a negative declaration of knowledge. In Italian, stating that someone didn't know something removes the absolute certainty of the fact, introducing an element of subjectivity to the secondary clause. This triggers the subjunctive mood.

Why is the imperfect subjunctive (fosse) used rather than the present subjunctive (sia)?

This is due to the sequence of tenses. The main verb (sapeva) is in the past tense. Because the bewilderment was happening at the exact same time the doctor didn't know about it, we must match the past timeframe of the main clause by using the imperfect subjunctive (fosse).

If the doctor did know, would we still use the subjunctive?

No. Positive statements of knowledge or certainty express facts and therefore trigger the indicative. If the sentence were positive, you would say: Il medico sapeva che il mio smarrimento era così profondo. It is specifically the negative word non that shifts the phrase into the subjunctive.

What is the literal meaning behind the word smarrimento?

Smarrimento is a noun derived from the verb smarrire, which means to lose or misplace something. When applied to a person's emotional state, it vividly describes a feeling of profound disorientation, bewilderment, or the sensation of being completely lost.