Mark, one of our readers, requests a discussion of the difference between systematic and systemic.
Both adjectives derive from the noun system which, in late Latin, meant a musical interval, that is, a difference in pitch between two notes.
While retaining its original meaning, the Latin word came to mean, in addition:
a union of several metres into a whole, the universe, body of the articles of faith, an organized whole, government, constitution, and a body of men or animals
systematic [sis tuh MA tik]
In its most common use by the general speaker and writer, the adjective systematic means “Arranged or conducted according to a system, plan, or organized method.” A novelist, for example, may have a systematic method of organizing note cards.
More specialized meanings of systematic occur in the writings of philosophers, statisticians, and biologists, as the following examples from the OED illustrate:
When the same words are used in sentences which express different kinds of propositions, yet in each case the usage is significant, then these words are said to have ‘systematic ambiguity’… This ambiguity is systematic because it can be formulated according to a rule.
an error with a non-zero mean, so that its effect is not reduced when observations are averaged.
Pertaining to, following, or arranged according to a system of classification; of or pertaining to classification, classificatory.
systemic [sis TEM ik]
Note: Beware the pronunciation. I once heard a radio reporter pronounce it as “sus tee mik.”)
The adjective systemic is chiefly a scientific term meaning “belonging to, supplying, or affecting the system or body as a whole.” It is often used to refer to a condition that affects the nervous system in particular.
Read the labels on your gardening supplies. If your herbicide, insecticide, or fungicide is described as “systemic,” it kills the pest you’re after by entering its system and making its way throughout the plant’s or animal’s tissues.
In 1961 M. A. K. Halliday came up with the term “systemic grammar” to describe a method of linguistic analysis. The rationale for the use of “systemic” instead of “systematic” in this instance eludes me, but then, so does the meaning of this OED example which records the use of the expression:
The grammar that assigns to sentences structures like the one in Fig. 1 is generative fusion of elements of American-style immediate-constituent analysis, European-style dependency theory, and British-style systemic grammar.
Unless you are referring to an organism, you probably want the word systematic.