Define the fourth heart sound. It is heard right before S1 late in diastole and sounds like ventricular filling. Sounds like da LUB-dub. It can be heard on the apex in the left lateral position. It is normal in people over the age of 40-50. Usually heard after exercise with no CV disease. Abnormal sounds like an atrial gallop.
Define subset. subset synonyms, subset pronunciation, subset translation, English dictionary definition of subset. n. A set contained within a set. n 1. maths a. a set the members of which are all members of some given class: A is a subset of B is usually written AâB b.... Subset - definition of subset by The Free Dictionary
A set A is said to be a subset of a set B, if every element of A is also an element of B. In other words, $A \subset B$ if whenever $a \in A$, then $a \in B$. It is often convenient to use the symbol $\Rightarrow$ which means implies. Using the symbol $\Rightarrow$, we can write the definition of subset as follows: $A \subset B$ if $a \in A \Rightarrow a \in B$. We read it as A is a subset of B if a is an element of A, which implies that a is also an element of B.