Depends on the context. Technically, phosphorus is an element (P), and phosphate is a molecular anion (PO4_3-), part of phosphoric acid (H3PO4). In (medical) diagnostic testing, they're often used...
Serum is the liquid portion of blood AFTER it has clot. Compared to plasma, which is the liquid portion of blood before it clots. The difference is the absence of fibrinogen in serum.
serum is a clear yellowish fluid obtained after separating blood into into its solid and liquid components after it ha been allowed to clot. Serum contains antitoxins. The introduction of serum in...