Sister, from the Old English word sweoster and cognate with the Latin term soror, means not only “a female with one or more parents in common” but has also come, by extension, to refer to a woman with whom one has a bond or a common interest.
It also applies to national or racial commonality, as in the term “soul sister,” which in American English describes a black female. In addition, it can refer loosely to a female relative or a girl or woman with whom one has an affinity, including among feminists; it is also slang for referring to a female in general. In religious contexts, it denotes a female member of a religious order. Because nuns often served as nurses, in British English, sister is still synonymous with nurse.
Sis is an informal abbreviation, often used in direct address by a sibling, as is sissy, though this term acquired the pejorative connotation of an effeminate man. The quality of being a sister, literally or figuratively, is sisterhood; the term also applies to a society of sisters, such as a religious community of women.
Sister-german is a technical legal term pertaining to the default definition of sister—“a woman or girl who has both of the same parents as a given person,” as opposed to a half sister, who shares only one parent, or a stepsister, the daughter of a stepparent. (The term german, from the Latin word germanus, means “having the same parents” and is unrelated to the proper noun referring to a person from Germany.)
A blood sister is literally a sister by birth or figuratively someone with whom one shares a bond of loyalty; this term, inspired by “blood brother,” alludes to the ceremonial exchange of blood between two men, often by mingling blood at the point of a slight self-inflicted wound. “Big sister” refers to one’s older female sibling or to a woman who mentors a girl to whom she is not related.
Phrases that include the word include “sister act,” a term from vaudeville describing a variety act consisting of two or more sisters, and “sob sister,” slang for an advice columnist or a writer of sentimental stories supposed to appeal primarily to women, alluding to the emotional reaction expected of female readers when reading such material. “Weak sister” is an allusion to the supposed inferiority of women that refers to an ineffectual, unreliable, or weak person in a group.
Meanwhile, a sister language is one in the same language family, such as Spanish as compared to Portuguese and vice versa, while a sister city is a municipality that has established a cultural-exchange connection with a city in another country. In construction, to sister is to strengthen a structural element by attaching a similar component to it.
In carpentry, if you reinforce a joist or a rafter by adding another one alongside it, that is called “sistering”, and the added joist or rafter is called a “sister”.
Note: “’sob sister’, slang for an advice columnist…”
In Britain, there is a closely-related term for this: an “Agony Aunt.”
This aunt receives and publishes letters rather like “My man has been having an affair with the Countess of Prestwick, and I am suffering so horribly. I can’t ignore it, but if I go public with it, nobody will believe me and I will become an outcast! What should I do?” Then the Agony Aunt adds her advice in the newspaper, tabloid, or magazine.” An Agony Aunt – much more serious that Abigail Van Buren or Ann Landers!
In modern German, “the sister” is “die Schwester”. Then sourcing from the Middle Ages and the Renaissance, there is the word “Krankenschwester” = “Sister to the sick”, where “Krank” is the German term for sickness, or just being broken down. Thus “das Krankhaus” is a hospital, and sisters from Catholic orders used to work there. “Krank” is also the direct ancestor of the adjective “cranky”, and in “You must be feeling cranky today.”
When men started going into nursing in German-speaking countries, “Krankenschwester” obviously would not do. The verb “pflegen” means “to take care of”, so a male nurse became “der Pfleger”. Then to close the circle, some modern-thinking female nurses started calling themselves, “die Pflegerin”, where “in” is an all-purpose female ending for nouns: “der Lehrer” (a teacher) & “die Lehrerin” (a female teacher), “die Professorin”, “die Fueherin” (female driver or leader), “der Arzt” & “die Arztin” (physicians), just like in Spanish they have “El doctor” & “La doctora”.
I was studying engineering while my sister was in pre-med. A favorite sentence of mine was “Meine Schwester wird Arzt,” = “My sister is becoming a doctor,” but to me is seemed more like “My sister is a weird doctor.”
If is interesting that the spellchecker here accepts all sorts of German words, if they are spelled correctly, as well as English words.
When two ships or submarines are built to the same design, they are called “sister ships”, and the whole set is called a “class”. For example, the “Spruance” class of destroyers in the U.S. navy had 31 sister ships in it, and the USS “Spruance” and the USS “Aaron Ward” were sister ships, like it or not. The “Arleigh Burke” class of destroyers has over 60 ships in it, and it is still growing, with more being built in Maine and in Mississippi.
This class contains one that is a sister in more ways than one: the USS “Hopper” (DDG 70), which was named for Rear Admiral Grace Hopper of the U.S. Navy. Admiral Hopper was a world-renowned expert in digital computers, and she was one of the developers of the first higher-level programming language for computers: COBOL. This class is known for having ships named for people who were not warriors but rather experts in other fields, such as the “Hopper” and the USS “Momsen” which was named for “Swede” Momsen, a great submarine-rescue expert for the Navy during the 1930s – 1950s. He and his team rescued a lot of sailors from sunken submarines.
The classic ocean liners “Queen Mary” and “Queen Elizabeth” were sister ships, and the “Queen Mary” still exists in Long Beach harbor, California. Sadly, the “Queen Elizabeth” was ravaged in an inferno in Hong Kong, and her remains had to be scrapped.
The “Titanic” also had sister ships, and sadly one of those was destroyed in the Mediterranean Sea during World War I, so that class of sister ships had a very sad history.
Two stars in a mutual orbit around one another can be said to be “sister stars”, and in the unlikely event of two planets like this, “sister planets”. (not brothers)
Two or more chemical elements that are VERY similar to one another chemically are “sister elements”. Examples of these include zirconium and hafnium; neodymium and praseodymium (both useful in special lasers); tantalum and niobium; uranium, neptunium, and plutonium; platinum and palladium; and iridium and osmium; ruthenium and rhodium.
In Greek mythology, King Tantalus (tantalum) was the father of Princess Niobe (niobium). So, there was a daughter involved.
In nuclear engineering, zirconium and hafnium have opposite nuclear properties, despite their chemical similarity.
Zirconium is quite transparent to neutrons because it absorbs so very few of them. On the other hand, most isotopes of hafnium absorb neutrons avidly, and so hafnium is used in the control rods that are used to control nuclear reactors or to scram them (shut them down). Other elements that are good in these are boron, cadmium, silver, yttrium, ytterbium, and other rare earths.
Chemical elements named for women, and genuine sisters in a way:
niobium, element #41, named for Princess Niobe
cerium, element 58, named for the new asteroid Ceres, which in turn had just been named for the Greek goddess of grain & the harvest. Her name is the origin of the word “cereal”.
europium, element 63, named for Europe, which was in turn named for the Roman goddess Europa.
curium, element-96, named for Marie & Pierre Curie, who had discovered the radioactive elements polonium and radium, and many other things about radioactivity and X-rays. Their daughter Irene Joliet-Curie was also a winner of the Nobel Prize, sharing hers with her husband, Frederick Joliet-Curie.
meitnerium, element 109, named for the Swedish-German physicist Lisa Meitner. Besides her discoveries in nuclear physics, Dr. Meitner did a very smart thing when Hitler came to power: She left Germany and went back to her native Sweden, taking her nephew, Dr. Otto Frisch, with her. They both had Jewish backgrounds, too.
If you think of the moon as being female, then selenium was named for the moon, “selene” in Greek.
As for Mother Earth, tellurium, is named for the Earth, from the Latin word “tellus” for the Earth. “Tellus” is related to such words as terra, terrain, terrestrial, and territory.