Pronunciation: [ˈə͡ʊk ˈapə͡l] (IPA) 
The spelling of the word "oak apple" can be explained using the IPA phonetic transcription. The first syllable "oak" is pronounced as /oʊk/ which represents the long vowel sound "o". The second syllable "apple" is pronounced as /ˈæp(ə)l/ which begins with the stressed short vowel "a" and ends with the consonant blend "pl". "Oak apple" refers to a type of gall produced by oak trees and is commonly used in natural medicines.
Oak apple refers to an abnormal growth commonly found on oak trees, caused by certain species of gall wasps and other insects. This term is specifically used to describe the spherical or apple-shaped gall formation that develops on the branches or leaves of oak trees. The growth appears due to a reaction between the plant tissue and the chemicals secreted by the gall wasp during egg-laying.
The oak apple gall is typically green initially, resembling a small fruit, but gradually turns brown or black as it matures. It is composed of dense, spongy plant tissue that provides protection and sustenance for the developing insect larvae inside. These galls can vary in size, ranging from a few millimeters to several centimeters in diameter.
Oak apples are considered a type of plant gall, which are abnormal plant tissue growths triggered by insect activity or bacterial or fungal infections. Despite their appearance, oak apples do not pose significant harm to oak trees, as they generally do not cause extensive damage to the overall health of the tree. However, severe infestations may affect the tree's growth and vigor, especially if occurring annually or in great numbers.
In some cases, oak apples are also sought and collected by individuals for their unique nature and aesthetic value. They have been utilized in natural crafts, traditional medicine, and even as components of certain dyes.
A kind of gall, being a spongy exerescence on oak-leaves and tender branches.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The etymology of the word "oak apple" can be traced back to the Old English word "āc" (meaning oak) and the Old English word "æppel" (meaning apple). The term "oak apple" refers to the gall (or growth) that forms on oak trees as a result of being stung by certain insects, particularly Cynips gall wasps. The appearance of these galls may resemble small apples, hence the term "oak apple" was coined.
