A polymer is a molecule, made from joining together many small molecules called monomers. The word "polymer" can be broken down into "poly" (meaning "many" in Greek) and "mer" (meaning "unit"). This shows how the chemical composition of a polymer consists of many smaller units (monomers) bonded together into a larger molecule. A chemical reaction bonding monomers together to make a polymer is called polymerization.
Some polymers are natural and made by organisms. Proteins have polypeptide molecules, which are natural polymers made from various amino acid monomer units. Nucleic acids are huge natural polymers made up of millions of nucleotide units. Cellulose and starch (two types of carbohydrate) are also natural polymers made up of glucopyranose monomer bonded together in different ways. Rubber is a mixture of polymers. Plastics are man-made polymers. Many fibers are made of polymers.
If the "units" called monomers in a polymer are all the same, then the polymer is called a "homopolymer". Homopolymers are named by adding the prefix poly- before the monomer name from which the polymer is made. For example, a polymer made by bonding styrene monomer molecules together is called polystyrene.
If the monomers are not all the same, the polymer is called a "copolymer" or a "heteropolymer".
Many polymer molecules are like "chains" where the monomer units are the links. Polymer molecules can be straight-chain, have "branching" from the main chain, or "cross-linking" between chains. As an example of cross-linking, sulfhydryl (-S-H) groups in two cysteine amino acid units in polypeptide chains can bond together to make a disulfide bridge (-S-S-) joining the chains together.
Medium
Medium might mean:
Phrase
A "phrase" is a group of words that adds meaning to a sentence. A phrase is not a sentence because it is not a complete idea with a subject, verb and a predicate.
In English there are five different kinds of phrases, one for each of the main parts of speech. In a phrase, the main word, or the word that is what the phrase is about, is called the "head." In these examples, it is printed in "bold". The other words in the phrase do the work of changing or "modifying" the head.
In a 'Noun phrase', one or more words work together to give more information about a noun.
In an Adjective phrase, one or more words work together to give more information about an adjective.
In a Verb phrase, one or more words work together to give more meaning to a verb. In English, the verb phrase is very complex, but a good description of its many forms can be found here.
In an Adverb phrase, one or more words work together to give more information about an adverb.
In a Prepositional phrase, one or more words work together to give information about time, location, or possession, or condition. The preposition always appears at the front of the phrase (preposition = pre-position).
Preposition
Prepositions often describe the position of something, the time when something happens or the way in which something is done. The prepositions "of", "to" and "for" have other functions.
Prepositions may sometimes be used to end sentences. For example, "What did you put that there for?" (better English is the alternative: "Why did you put that there?") Example 2: "A pen is a device to write with" (better English is "A pen is a writing device"). In general, because they are links, prepositions belong in the middle of sentences, rather than at the end.
The table below shows some examples of how prepositions are used in sentences.
Here is a list of common prepositions:
Pronoun
A pronoun is traditionally a part of speech in grammar, but many modern linguists call it a type of noun. In English, pronouns are words such as "me, she, his, them, herself, each other, it, what".
Pronouns are often used to take the place of a noun, to avoid repeating the noun. For example, instead of saying
it is easier to say
When a pronoun replaces a noun, the noun is called the antecedent. For example, in the sentence: "The dog that was walking down the street", the relative pronoun is the word that referring back to the antecedent, the word 'dog'. In the sentence "The spy who loved me", the relative pronoun is the word 'who' and its antecedent is the word 'spy'.
Pronouns are different from common nouns because pronouns normally do not come after "article"s or other "determiner"s. For example, people do not say "the it". Pronouns rarely come after adjectives. They are also different because many of them change depending on how they are used. For example, "we" is a 'subject' in grammar, but the word changes to "us" when used as an object.
Pronouns are the same as nouns because they both change for number (singular & plural), case (subject, object, possessive, etc.), and gender (male, female, animate, inanimate, etc.) Nouns and pronouns can be used in almost all the same places in sentences, and they name the same kinds of things: people, objects, etc. Even though they can not normally come after determiners, or adjectives, neither can proper nouns.
There are four kinds of pronouns: personal, reciprocal, interrogative, and relative.
This table shows all the personal pronouns in English that are commonly used today.
A subject pronoun can replace a noun that is the subject of a sentence. Refer to the table above; the subject pronouns are: I, You, He, She, It, We, They. An object pronoun can replace a noun that is the object of a sentence. A possessive pronoun shows who or what a noun belongs to.
Another type of personal pronoun is called the 'reflexive pronoun'. Reflexive pronouns are the words ending in '-self' or '-selves', such as: "myself, itself, themselves".
"It" and its other forms "its", and "itself" only refer to objects, not people. "They" and its other forms "them", "their", and "theirs" can be used as a singular, for a person whose gender is unknown at the time, or for a person who does not identify with either the "she/her" or "he/him" pronouns. For example: "The patient will be told how much "they" will be required to pay."
Adverb
An adverb is a word used to tell more about a verb, and it almost always answers the questions "how?", "when?", "where?", "how often?", and "in what way?". Words like "slowly", "loudly", "carefully", "quickly", "quietly" or "sadly" are all adverbs. Adverbs usually, but not always, end in "-ly".
Examples of adverbs in a sentence (with the adverb in italics): that is a weird word and is seen differently
An adverb can also modify (describe) an adjective or another adverb
Examples:
In the first two examples the word 'well' is an adverb. In the last example, it is an adjective. This is one example in which the same word can be both an adjective and an adverb but not in the same sentence.
As a rule, the same word can play different roles but not in the same sentence. It all depends on what the word is doing in the sentence. It could be a noun, an adjective, an adverb, a verb, etc. Example: take the word 'cool'. In the sentence, "he walks cool", the word 'cool' is an adverb. In the sentence, "cool the hot dish", the word 'cool' is a verb. In the sentence, "it is a cool evening", the word 'cool' is an adjective. In the first example, "he walks cool", the word 'cool' really means 'coolly' as in "play it cool" (do not get excited; be calm).
Most adverbs are formed by adding ly to the end of an adjective. To see 100 adjectives used in Basic English, click here ---> : adjective
Sunday
Sunday is one of the seven days of the week. It is part of the weekend, along with Saturday. Sunday is the Sabbath or day of worship for most Christians (for example, Easter is celebrated on Sunday). Sunday is the beginning of the week in the United States, but is the end of the week in the United Kingdom.
Ottawa