"But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil." — Jesus Christ (Matthew 5:37, KJV)
Semantics (from Greek sêmantiká, neuter plural of sêmantikós) is the study of the meaning of a word, phrase, sentence, or text. Here emphasis will be placed on the pejorative sense of the term semantics that is rooted in popular use (i.e., when people talk about the way that language can be manipulated in order to mislead the public). For example and according to the Global Language Monitor (GLM) "change" was the most-used term during the U.S. Presidential campaign of 2008.  Today many are asking, what did the term "change" really mean? Still others are asking, what's the point of such a question? Is this a good question or is the point of such a question just a matter of applied semantics (i.e., purely a petty or paltry verbal pretense), bearing no relationship to anything in the real world?
Just A Matter of Applied Semantics?
"Woe to them that call evil good, and good evil; that put darkness for light, and light for darkness; that put bitter for sweet, and sweet for bitter!" — The Old Testament Prophet Isaiah (Isaiah 5:20, KJV)
Applied Semantics is the study and application of semantics which have many uses (e.g., advertising, text analysis, etc.). According to Ob.Gyn. News, "Ulipristal Acetate" (i.e., ellaOne) is an emergency contraceptive effective for up to 5 days after unprotected intercourse.  This drug contains a hormone that delays ovulation and alters the environment inside the uterus to prevent implantation of a zygote or embryo. Apparently, the drug fails when a woman is "already pregnant" or when "implantation" has occurred. Did you catch that? A woman is now pregnant when "implantation" has occurred instead of at the moment of "conception" or "fertilization". In 1959 Dr. Bent Boving, at a Planned Parenthood symposium, seductively proposed the word "conception" should mean "implantation" instead of "fertilization" and effectively gave birth to the illusion of a "pre-embryo".  This concept allows drugs to be described as conception "preventers" rather than "destroyers" of an "established pregnancy" or an abortifacient. In 1965 the American College of Obstetricians and Gynecologists (ACOG) embraced Boving's idea and redefined conception to mean: "implantation of an ovum".  In 2000 Stedman's Medical Dictionary followed ACOG and now conception means "implantation".  Is this "change" in our language just a matter of applied semantics or a deliberate attempt to mislead the public?
Semantics Or Truth, Which Is To Be Master?
"And ye shall know the truth, and the truth shall make you free." — Jesus Christ (John 8:32, KJV)
According to the Nomina Embryologica Committee there is no such thing as a "pre-embryo". The term is scientifically inaccurate, misleading and a complete myth. There is, rather, an already existing, new living human embryo, a human being that begins to exist immediately at fertilization or cloning.  Could this "change" be just an innocent matter of semantics? Why would anyone want to redefine the term conception? Perhaps Humpty Dumpty  has already answered this question: "When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean — neither more nor less." "The question is", said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which [or 'who', referring to those that do and those that do not choose to "make words mean so many different things"] is to be master — that's all." 
Brothers, we really need to talk.
1. The Global Language Monitor (GLM) documents, analyzes and tracks trends in language the world over, with a particular emphasis upon Global English (http://bit.ly/cMDLzR).
2. FDA Approves EC Effective Up to 5 Days, Ob.Gyn. News September 2010 (http://bit.ly/9Qnzmo).
3. See American Life League article (http://bit.ly/bYxfP4) and "Implantation Mechanisms," in Bent Boving (ed. C. G. Hartman). 1963. Mechanisms Concerned with Conception, New York: Pergamon Press. p. 386.
4. See Answers In Genesis article (http://bit.ly/dfL071). Terms Used in Reference to the Fetus. ACOG Terminology Bulletin 1, September 1965. Chicago: American College of Obstetrics ad Gynecology. The ACOG definition was refined in 1972, changing the word ovum to blastocyst, but maintaining that conception, and therefore pregnancy, begins at implantation.
5. See Answers In Genesis article (http://bit.ly/dfL071). In the 26th edition (1995) of Stedman's Medical Dictionary, conception was defined as the "act of conceiving, or becoming pregnant; fertilization of the oocyte (ovum) by a spermatozoon to form a viable zygote." In the 27th edition (2000) of Stedman's Medical Dictionary, conception is defined as follows: "Act of conceiving; the implantation of the blastocyte in the endometrium."
6. According to Dianne N. Irving, Ph.D.'s article "A One-Act Play: Crippled Consciences and the Human Embryo" (http//bit.ly/c5Bnkl), quoting directly from human embryologists, "The term 'pre-embryo' is not used here for the following reasons: (1) it is ill-defined because it is said to end with the appearance of the primitive streak or to include neurulation; (2) it is inaccurate because purely embryonic cells can already be distinguished after a few days, as can also the embryonic (not pre-embryonic!) disc; (3) it is unjustified because the accepted meaning of the word embryo includes all of the first 8 weeks; (4) it is equivocal because it may convey the erroneous idea that a new human organism is formed at only some considerable time after fertilization; and (5) it was introduced in 1986 'largely for public policy reasons' (Biggers)." ... Just as postnatal age begins at birth, prenatal age begins at fertilization." [O'Rahilly and Muller 2001, p. 88] ... "Undesirable terms in Human Embryology": "Pre-embryo"; ill-defined and inaccurate; use "embryo". See O'Rahilly and Muller 2001, p. 12.
7. "Humpty Dumpty sat on a wall. Humpty Dumpty had a great fall. All the king's horses and all the king's men, couldn't put Humpty together again.", Opie and P. Opie, The Oxford Dictionary of Nursery Rhymes (Oxford: Oxford University Press, 1951, 2nd edn., 1997), ISBN 0-19-869111-4, pp. 213-5.
8. Through the Looking-Glass, by Lewis Carroll [Charles Dodgson]