  We propose a unified analysis of a whole spectrum of no-arbitrage conditions
for financial market models based on continuous semimartingales. In particular,
we focus on no-arbitrage conditions weaker than the classical notions of No
Arbitrage and No Free Lunch with Vanishing Risk. We provide a complete
characterisation of the considered no-arbitrage conditions, linking their
validity to the characteristics of the discounted asset price process and to
the existence and the properties of (weak) martingale deflators, and review
classical as well as recent results.
