Fertilisation (also known as conception, fecundation and syngamy), is the fusion of gametes to produce a new organism. [en.wikipedia.org/wiki/Fertilization]
Conception – the act of becoming pregnant; fertilization of an ovum by a spermatozoon [wordnetweb.princeton.edu/perl/webwn]; in reproduction, the point at which a sperm fertilizes an egg [www.ornl.gov/hgmis/publicat/genechoice/glossary.html]; the beginning of pregnancy, when the sperm cell from the father joins with the egg cell from the mother [hes.ucfsd.org/gclaypo/repro/vocab.html]; the formation of a viable zygote by the union of a spermatozoon and an ovum; fertilization [The American Heritage® Stedman’s Medical Dictionary].
Let us start with commonsense. Conception generally means the event that occurred at the beginning of something. You do not need to be a scientist to conclude that this event in the womb (the beginning of something) is the creation of the new organism, which is called zygote. And what do we call this process where zygote is created? It is fertilization. The moment an ovum is fertilized by a spermatozoon, conception occurs; that is, a new entity comes into being; the two become one.
Why is it such a big deal? Because there is a big lie that is now being accepted worldwide regarding the humanity of a zygote; a malicious manipulation of the meaning of medical and even English terms to mislead everybody and to justify all actions that destroy or endanger human life in its earliest stage, including contraception, in vitro fertilization, and embryonic stem cell research. What some so-called medical people did is they have redefined the words conception, pregnancy, and abortion all in relation with the term fertilization. They claim that conception, and not fertilization, is the beginning of pregnancy, as if these are two different things. According to these people, conception refers to the implantation of the blastocyst to the wall of the uterus, and so they say, preventing implantation is not a form of abortion since there is no conception yet until the embryo is implanted. Maybe it sounds plausible and it has actually deceived many, even within the medical community, but it is not that neat. The beginning of one thing means the cessation of another. There is no conception or creation that happens during implantation; it is just another stage of pregnancy. It is the zygote that results from the fusion of the ovum and the spermatozoon that is a new creation; the one that is conceived. Fertilization is the process where the two gametes from the male and the female cease to be and become a whole new existence — a human being. Implantation only refers to the event where the human embryo is attached to the uterine wall in order to survive, and as have already said, it does not create or conceive anything.
Fertilization, and not implantation, is conception. It is the earliest stage of pregnancy. Once the egg cell (ovum) is fertilized, the woman is pregnant. Therefore, every action that prevents implantation or destroys the fertilized egg is no less than an abortion — killing of a human being.