So then, let me continue with my mini-lecture on music terminology. Of course, I learned all about perfect pitch, the one talent those singers and musicians I used to swoon at all have. Then my dear professor introduced another term, which became dearly attached to me since it described my musical condition. The term is tone deafness.
Tone what? Tone deaf? Is there such?
Yes, there is such. I actually believed with all of my heart that I was tone deaf, until I learned that only 6% of the entire population has it. It is just generally used to describe those who sing out of tune. This common use of tone deafness refers to a person’s inability to reproduce tones they hear accurately, which is most often caused by lack of musical training or education and not actual tone deafness (that includes my case). The real meaning of tone deafness, however, is the inability to discriminate between musical notes. Being tone deaf is having difficulty or being unable to correctly hear relative differences between notes.
This relative difference between notes is associated with relative pitch, and ability of it as with other musical abilities, appears to be inherent in healthy functional humans. While someone who is unable to reproduce pitches because of a lack of musical training would not be considered tone deaf in a medical sense, the term might still be used to describe them casually. Someone who cannot reproduce pitches accurately, because of lack of training or tone deafness, is said to be unable to “carry a tune.” Tone deafness affects ability to hear pitch changes produced by a musical instrument and/or the human voice.
However, tone deaf people seem to be only disabled when it comes to music, and they can fully interpret the intonation of human speech. Tone deaf people often lack a sense of musical aesthetics, and much like a color blind person would not be apt to appreciate colorful visual art, some tone deaf people cannot appreciate music. Tone deafness is also associated with other musical-specific impairments such as inability to keep time with music (the lack of rhythm), or the inability to remember or even recognize a song. These disabilities can appear separately but some research shows that they are more likely to appear in tone deaf people.
Experienced musicians such as W. A. Mathieu have addressed tone deafness in adults as correctable with training. Tone deafness is also known variously as amusia, tune deafness, dysmelodia and dysmusia. (Thanks Wikipedia.) 
Hope you enjoyed learning something new again musically!