The word abortion comes from the Latin abortio, which means to abort, miscarry, deliver prematurely. The Latin word abortus means "miscarriage, premature, untimely birth". In medicine abortion means ending a pregnancy prematurely.
An abortion can happen spontaneously as a result of complications during a pregnancy, or it can be induced. An induced abortion carried out to preserve the health of the mother (gravida) is a therapeutic abortion. An abortion carried out for any other reason is called an elective abortion.
Abortion - is the act of terminating pregnancy. It is any action with the aim of expelling the fetus or embryo inside a woman’s womb before the end of the natural period of development. (Termination intentional).
Miscarriage - generally used to mean a spontaneous termination of pregnancy (Termination not intentional). Or due to physical injury of the woman or as a result of internal biomedical factors.
Therapeutic abortion - induced termination of pregnancy to protect the mother's health or life.
According to WHO, every year in the world an estimated 40-50 million women faced with an unplanned pregnancy decide to have an abortion. This corresponds to approximately 125,000 abortions per day.  
Total number of abortions in the U.S. 1973-2011: 54.5 million+
“And do not kill your children for fear of poverty. We provide for them and for you. Indeed, their killing is ever a great sin.” Qur’an.Surah Al-Isra 17:31.
Say, "Come, I will recite what your Lord has prohibited to you. [He commands] that you not associate anything with Him, and to parents, good treatment, and do not kill your children out of poverty; We will provide for you and them. And do not approach immoralities - what is apparent of them and what is concealed. And do not kill the soul which Allah has forbidden [to be killed] except by [legal] right. This has He instructed you that you may use reason." Qur’an.Surah Al-Anaam 6:151.
"O Prophet! When believing women come to thee to take the oath of fealty to thee, that they will not associate in worship any other thing whatever with God, that they will not steal, that they will not commit adultery (or fornication), that they will not kill their children, that they will not utter slander, intentionally forging falsehood, and that they will not disobey thee in any just matter,- then do thou receive their fealty, and pray to God for the forgiveness (of their sins): for God is Oft-Forgiving, Most Merciful.” Qur’an.Surah Al-Mumtahina 60:12.
Before these Noble aayaath were revealed, the pagan Arabs (before the prophethood of Muhammad ﷺ used to literally bury their daughters at the age of 4 or less alive in the desert, because (1) Daughters' birth brought shame to the family, and the mother had "defied" the husband's demand to bear him a son; or (2) The family was so poor, the parents would fear that someday they would have to sell their children as slaves to others.
While abortion clinics did not exist 1500 years ago, but people as it is apparent today, were able to cause a woman to miscarry her child by either striking her in the tummy, causing her to have lots of fear, or mess with the vagina until the child is pulled out.
Narrated Abdullah: Allah's Apostle ﷺ, the true and truly inspired said, "(as regards your creation), every one of you is collected in the womb of his mother for the first forty days, and then he becomes a clot for an other forty days, and then a piece of flesh for an other forty days. Then Allah سبحانه و تعالىsends an angel to write four words: He writes his deeds, time of his death, means of his livelihood, and whether he will be wretched or blessed (in religion). Then the soul is breathed into his body. Sahih Al-Bukhari, Vol 4:549, Sahih Al-Bukhari, Vol 8:593 
Scientific Discoveries that confirm the above Hadith
Shaykh Saalih al-Fawzaan (رحمت الله) said:
Aborting pregnancy is not permissible. If a woman is pregnant the pregnancy must be protected, and it is haraam for the mother to harm this pregnancy or to put any kind of pressure on it, because it is a trust that Allah سبحانه و تعالى has placed in her womb and it has rights, so it is not permissible to mistreat it, harm it or destroy it. The shar’i evidence indicates that it is haraam to abort pregnancy.
The fact that she cannot give birth without surgery is no justification for abortion. Many women cannot give birth without surgery, so this is not an excuse to abort the surgery.
If the soul has been breathed into this foetus and it has begun to move, then she aborted it after that and it died, then she is regarded as having killed a soul, so she must offer expiation by freeing a slave. If that is not possible then she must fast for two consecutive months as repentance to Allah سبحانه و تعالى. That applies if it was four months old, because in that case the soul had been breathed into it. If she aborted it after that, then she must offer expiation as described above. This matter is very serious and cannot be taken lightly. If she could not bear the pregnancy because she is sick, then she should take medicines that prevent pregnancy before it begins, such as taking pills to delay getting pregnant until she regains her health and strength. Al-Muntaqa 5/301, 302.
Shaykh Muhammad ibn Ibraaheem رحمت اللهsaid: As for trying to abort a pregnancy, that is not permissible so long as the death of the foetus in utero is not proven; if that is proven then it is permissible. Majmoo’ Fataawa al-Shaykh Ibn Ibraaheem 11/151.