Notional (adjective)

1. Existing in the mind as an idea or concept, but not having a physical or concrete existence.
2. Relating to or being an estimate, especially a rough one, rather than a precise or actual value.

Origin:

From the latin word 'notionem' meaning an idea or concept.

Examples:

1. The plan was only a notional idea, it had not been implemented yet.
2. The notional value of the company was based on future projections and assumptions.
3. His understanding of the situation was only a notional one, he had no actual knowledge.
4. The notional amount of the loan was determined by the value of the collateral.
5. The notional cost of the project was estimated to be much lower than the actual cost.