Readability grades

Style understands cpp(1) #line lines for being able to give precise locations when printing sentences.

Kincaid formula

The Kincaid Formula was developed for U.S. Navy training manuals; it ranges in difficulty from 5.5 to 16.3. It is probably best applied to technical documents, because it is based on adult training manuals rather than school book text. Dialogs (often found in fictional texts) are usually a series of short sentences, which lowers the score. On the other hand, scientific texts with many long scientific terms are rated higher, although they are not necessarily harder to read for people who are familiar with those terms.

Kincaid = 11.8*syllables/wds+0.39*wds/sentences-15.59

Automated Readability Index

The Automated Readability Index is typically higher than Kincaid and Coleman-Liau, but lower than Flesch.

ARI = 4.71*chars/wds+0.5*wds/sentences-21.43

Coleman-Liau Formula

The Coleman-Liau Formula usually gives a lower grade than Kincaid, ARI and Flesch when applied to technical documents.

Coleman-Liau = 5.88*chars/wds-29.5*sent/wds-15.8

Flesch Reading Ease formula

Developed by Rudolph Flesch in 1948, the Flesch Reading Ease formula is based on school texts covering grades 3 to 12. It is widespread, especially in the USA, because it is computed easily and produces good results. The index ranges from 0 (hard) to 100 (easy). Standard English documents average around 60 to 70. Applying it to German documents gives poor results because of the different language structure.

Flesch Index = 206.835-84.6*syll/wds-1.015*wds/sent

Fog Index

The Fog index was developed by Robert Gunning. Its value is a school grade. The “ideal” Fog Index level is 7 or 8. A level above 12 indicates the writing sample is too hard for most people to read. Texts less than 100 words will not produce meaningful results. Note that a correct implementation would not count words of three or more syllables that are proper names, combinations of easy words, or made three syllables by suffixes such as –ed, –es, or –ing.

Fog Index = 0.4*(wds/sent+100*((wds >= 3 syll)/wds))

Lix formula

The Lix formula developed by Björnsson from Sweden is very simple and employs a mapping table as well:

Lix = wds/sent+100*(wds >= 6 char)/wds

SMOG Grading

The SMOG Grading for English texts was developed by McLaughlin in 1969. Its result is a school grade.

SMOG Grading = square root of (((wds >= 3 syll)/sent)*30) + 3

It was adapted to German by Bamberger and Vanecek in 1984, who changed the constant +3 to -2.

Word usage

The word usage counts are intended to help identify excessive use of particular parts of speech.

Verb Phrases

The category of verbs labeled "to be" identifies phrases using the passive voice. Use the passive voice sparingly, in favor of more direct verb forms. The flag -p causes style to list all occurrences of the passive voice.

The verb category "aux" measures the use of modal auxiliary verbs, such as "can", "could", and "should". Modal auxiliary verbs modify the mood of a verb.

Conjunctions

The conjunctions counted by style are coordinating and subordinating. Coordinating conjunctions join grammatically equal sentence fragments, such as a noun with a noun, a phrase with a phrase, or a clause to a clause. Coordinating conjunctions are "and," "but," "or," "yet," and "nor."

Subordinating conjunctions connect clauses of unequal status. A subordinating conjunction links a subordinate clause, which is unable to stand alone, to an independent clause. Examples of subordinating conjunctions are "because," "although," and "even if."

Pronouns

Pronouns are contextual references to nouns and noun phrases. Documents with few pronouns generally lack cohesiveness and fluidity. Too many pronouns may indicate ambiguity.

Nominalizations

Nominalizations are verbs that are changed to nouns. Style recognizes words that end in "ment," "ance," "ence," or "ion" as nominalizations. Examples are "endowment," "admittance," and "nominalization." Too much nominalization in a document can sound abstract and be difficult to understand. The flag -N causes style to list all nominalizations. The flag -n prints all sentences with either the passive voice or a nominalization.