The Division teleostei (perfect bone), or simply teleosts, comprise the majority (>90%) of bony fish while the term pisces is general and may also include primitive fish, from my understanding. They are known for their reduction in bony elements, have radiated to nearly every waterbody and their ancestral lineage can be traced by ~200 mya. Neopterygii are ancestral to teleosts and originated nearly 350 mya. So, for practical purposes teleosts should be used in an evolutionary context when referring to fishes.

Pisces can be used as a term to refer to all fish, both cartilaginous and bony, including the sharks, skates and rays (catilaginous fishes), lungfishes and coelacanths (lobe-finned bony fishes) along with all the reay-finned fishes. The teleosts are the largest 'sub-group' within the ray-finned fishes.

I am agree with Malcolm

Thank you for your valuable ideas!

Series Pisces ( Romer, 1959 & Berg, 1940) is a general classification term for aquatic vertebrates and include all the members of the series. However, Teleost are specifically termed to those members which poses true bony skeleton ,fishes having true Fin rays, Spines.

I agree with Jose that ‘Pisces’ is not a scientific term in the sense of phylogenetic systematics. This term traces back to the times when it was believed that the vertebrates were formed by four classes, the Pisces, Amphibians, Reptiles and Mammals. We know that this classification is out-dated. As Jose pointed out, if the term ‘Pisces’ would define a taxonomic unit all vertebrates would be classified as fishes, including the tetrapods and us humans. But this problem is solved. We all are Vertebrata, a subphylum of the Chordata.

But the term Teleostei describes a monophyletic unit. Teleostei and tetrapods together comprise 98% of all extant vertebrate species. The Teleostei are a part of the Actinopterygii (ray-finned fish) and the tetrapods of the Sarcopterygii (lobe-finned fish). Each represent a very successful Bauplan, one in the water the other on land. If one likes to compare evolved Teleostei like the Acanthopterygii (perches, cichlids) with tetrapods these teleosts run through an evolutionary highway like the tetrapod Amniota (chicks, mice), the former in the water, the latter on land, finally ‘pushing everything aside’. Seemingly we are just lobe-finned fish having lost the fin-rays to be able to move out of the water and to adapt to a life on land.