As a follow-up to Tip #22, let’s look at the usage of “dependence” versus “dependency.”

Let’s start by referring to Merriam-Webster’s Unabridged Dictionary for definitions. These have been edited for content. I’ve only included the relevant definitions. As always, the end of the quoted material is denoted by the “∎.”

dependence

or dependance

noun

plural -s 

1 archaic:  the quality or state of being undecided or undetermined 

2a:  the quality or state of depending upon or being dependent upon something else 

2b:  the quality or state of being influenced, conditional upon, or necessitated by something else 

3:  reliance, trust 

<place dependence upon old and trusted friends> 

<for a knowledge of Celtic law … dependence must be placed mainly on the written records — John MacNeill> 

4:  something on which one relies :  the object of one’s trust 

<he was her sole dependence> 

<cotton was the earliest crop … but ultimately rice became the chief dependence — R. H. Brown> 

5a :  a drug addiction 

5b :  habituation 2b 

∎

These definitions are pretty straightforward and the Merriam-Webster examples demonstrate how these are normally used.

Note that the use of the alternate spelling (dependant; dependance) can vary from UK to US English depending on which dictionary you consult. Often “dependant” refers to the noun (a child may described as a dependant), whereas “dependent” usually refers to the adjective (dependent child). To further confuse the situation, in US English either spelling is often cited as correct for the noun 

(As noted in Tip #22),

Now let’s look at dependency as defined by M-W .

dependency

noun

1a:  dependence (definition 2) 

<their dependency on the crown of England — Francis Bacon> 

<dependency in the infant increases in evolutionary sequence — Weston La Barre> 

1b:  the condition of receiving assistance from the community for the necessities of life:  the condition of being on relief 

2:  something that is dependent or in dependence upon something else: such as 

2a :  something necessarily consequent upon something else 

4:  the state of having dependents 

<deferred from army service because of his dependency> 

∎

Although the definitions seem very close and M-W actually uses “quality or state” in the definition of dependence, let’s take a closer look and use another source.

 The Merriam-Webster Learners Dictionary puts a slightly different spin on the differences. Here are their definitions, edited for content and clarity.

Learner’s definition of DEPENDENCE 

: the state of being dependent: such as 

a: the state of needing something or someone else for support, help, etc. — + on or upon 

[noncount] 

The company was hurt by its dependence on government loans.

Our dependence upon foreign oil makes our economy vulnerable.

a harmful dependence on foreign oil

b: the state of being addicted to alcohol or a drug 

drug and alcohol dependence [=addiction, dependency]

— usually + on 

She eventually developed a dependence on the painkillers she was taking.

Learner’s definition of DEPENDENCY 

1: the quality of being dependent : dependence 

the country’s dependency on foreign oil

drug/chemical dependency [=addiction]

a dependency on foreign oil

2 : an area that is controlled by a country but that is not formally a part of it

∎

I think that for our discussion, the Learners Dictionary definitions make the primary distinctions between the two words pretty clear:

• Dependence refers to the state of being dependent. This can be in an abstract sense. Note that dependence is an uncountable noun (there is no plural form).

The team was hurt by their dependence on freelancers.

• Dependency refers to the actual quality (or reality) of being dependent. Note that dependency is a countable noun (there’s a plural form: dependencies).

The team’s dependency on freelancers was perceived as a negative.

The context in which they are each used should help make this clear.

Let’s look at examples.

In many cities, people have a dependence on public transportation.

In this usage we are referring to a specific aspect. In this usage it is uncountable and somewhat abstract.

If we wanted to talk about the population in general, we could say this:

This dependency on public transportation often determines where they choose to live.

People who are said to have an addiction, whether to a substance or a behavior, would be said to have a dependence.

When we refer to this situation, we would describe it as a dependency.

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