selection = The act or an instance of selecting or the fact of having been selected. One that is selected. A carefully chosen or representative collection of people or things. See Synonyms at choice. A literary or musical text chosen for reading or performance. Biology A natural or artificial process that favors or induces survival and perpetuation of one kind of organism over others that die or fail to produce offspring. selectivity = The state or quality of being selective. The degree to which an electronic receiver is selective. @from somewhere online

Although Devin's answer is quite correct, Selectivity more commonly (to me at least, as an Engineer) has a more technical meaning. Wikipedia lists a few of them http://en.wikipedia.org/wiki/Selectivity The one that I am most familiar with isn't even in that list! - It is the ability of an etchant to remove one target material, without etching another. So - my answer is that Selectivity can have a lot of meanings - and you would have to mention the context to know what it means.

Hi May, The difference between these two words is simple. Selectivity is a noun which describes the care and effort a person or group takes in making a choice. If they are very selective, they choose very carefully - if they are not very selective, they choose quickly and carelessly without thinking very much. These are the two types of selectivity, and sometimes we describe them as 'high' or 'low' selectivity, or talk about a high or low 'degree' of selectivity. In a sentence: The group thought hard about their choice, showing the selectivity of its members. What the group chooses is its selection - if I choose to order a bottle of beer, that bottle is my selection. It means the same thing as 'choice' in this usage. However, you could also talk about the 'selection process' - the things you do to make a decision - but you cannot say 'choice process.' I hope I haven't confused you! Don't be afraid to send me a message if I have and I will do my best to clear it up. Devin