Spelling in English compounds is not very reliable as well because they can have different spelling even in the same text,
e.g. war-ship, blood-vessel can be spelt through a hyphen and also with a break,
insofar, underfoot, headmaster, loudspeaker can be spelt solidly and with a break (textbook, phrase-book, reference book).
In Modern English:
a special type of compound words which are called block compounds, they have one uniting stress but are spelt with a break, e.g.` air piracy, `cargo module,` coin change,` penguin suit etc.
The semantic unity of a compound word is often very strong. (H. Paul, O. Jespersen, E. Kruisinga). In such cases we have idiomatic compounds where the meaning of the whole is not a sum of meanings of its components, e.g. ladybird (an insect), skinhead (a person), bluestocking (a person),
man-of-war (a war-ship) etc.
In nonidiomatic compounds semantic unity is not strong, e. g., airbus, to bloodtransfuse, astrodynamics, etc.
English compounds have the unity of morphological and syntactical functioning. (A. Smirnitsky – formal integrity): a shipwreck but (the) wreck of (a) ship. They are used in a sentence as one part of it and only one component changes grammatically, e.g. These girls are chatter-boxes. «Chatter-boxes» is a predicative in the sentence and only the second component changes grammatically.
There are two characteristic features of English compounds:
a) Both components in an English compound are free stems, i.e. they can be used as words with a distinctive meaning of their own. The sound pattern is the same except for the stresses, e.g. «a` green-house» and «a` green `house». Whereas in Russian compounds the stems are bound morphemes.
b) English compounds have a two-stem pattern, with the exception of compound words which have form-word stems in their structure, e.g. middle-of-the-road, off-the-record, up-and-doing etc.
The two-stem pattern distinguishes English compounds from German ones.
WAYS OF FORMING COMPOUND WORDS.
Compound words in English can be formed not only by means of composition but also by means of :
a) reduplication, e.g. too-too, and also by means of reduplication combined with sound interchange , e.g. rope-ripe,
b) conversion from word-groups, e.g. to micky-mouse, can-do, makeup etc,
c) back formation from compound nouns or word-groups, e.g. to bloodtransfuse, to fingerprint, etc ,
d) analogy, e.g. lie-in ( on the analogy with sit-in) and also phone-in, brawn-drain (drain of muscles)(on the analogy with brain-drain) etc.