The terms primary, secondary, and tertiary are used to describe successive stages or levels of something. After tertiary comes quaternary as the next term in sequence.
The sequence of terms primary, secondary, tertiary, and quaternary is commonly used to categorize successive levels or stages of development or formation. The origins of this terminology can be traced back to fields like geology, education, industry, and economics.
In geology, the terms are used to describe successive layers of rock. Primary rock is the original igneous or sedimentary rock. Secondary rock is formed from the weathering and erosion of primary rock. Tertiary rock is formed from secondary rock. Quaternary rock is the uppermost layer and includes alluvium, loess, tills, and glacial moraines.
In education, the terms originally referred to different levels of education. Primary education is elementary school. Secondary education is high school. Tertiary education is college, university, or graduate school. Quaternary education refers to post-graduate studies beyond a Masters degree.
In industry, the terms describe successive stages of production. Primary industry involves extracting raw materials. Secondary industry involves manufacturing. Tertiary industry involves services. Quaternary industry involves research, development, and information services.
In economics, the sectors describe different economic activities. Primary sector is agriculture and mining. Secondary sector is manufacturing. Tertiary sector is services. Quaternary sector is information services and knowledge economy jobs.
So in all of these examples, quaternary comes after tertiary as the fourth in order and sequence. Let’s explore the definitions and usage of these terms in more detail.
Definitions of the Terms
Here are the standard definitions of each term:
| Primary | First or highest in rank, quality, or importance; principal. |
| Secondary | Coming after first in order, place, time, etc.; following next after the primary or first. |
| Tertiary | Third in place or order; coming after secondary. |
| Quaternary | Fourth in order; coming after tertiary. |
As the definitions show, quaternary clearly comes after tertiary in sequence and order. Primary is first, secondary is second, tertiary is third, and quaternary is fourth.
Usage in Geology
In geology, the terms primary, secondary, tertiary, and quaternary describe the successive layers of rock that make up the Earth’s crust:
- Primary rock is the original igneous or metamorphic crystalline rock formed from the molten magma. Examples are granite and basalt.
- Secondary rock is formed by the weathering and erosion of primary rock. Examples are sandstone, shale, and conglomerate.
- Tertiary rock is formed from secondary rock through processes like compaction and cementation. Examples are limestone, coal, and chalk.
- Quaternary rock is the uppermost layer and includes alluvium, loess, tills, and glacial deposits.
Quaternary rocks are the most recent geological deposits and include sediments left behind by glaciers, rivers, wind, and rain. The Quaternary Period spans the last 2.6 million years of the Earth’s history, the time of the recent ice ages.
Usage in Education
In education, the terms historically referred to successive levels of education:
- Primary education – elementary schooling from kindergarten to 5th grade
- Secondary education – middle school and high school from 6th to 12th grade
- Tertiary education – post-secondary schooling including college, university, and graduate school
- Quaternary education – education beyond a Masters degree such as a PhD or post-doctoral work
So again, quaternary education comes after completion of tertiary education like a Bachelors or Masters degree. Quaternary education represents the most advanced study like doctoral research.
Usage in Industry
In industry and economics, the terms refer to successive sectors of activity:
- Primary industry – involves extracting raw materials like mining, agriculture, forestry, fishing, and quarrying.
- Secondary industry – involves manufacturing of finished products through processes like refining and construction.
- Tertiary industry – involves commercial services like retail, transportation, hospitality, education, healthcare, and finance.
- Quaternary industry – involves information services and knowledge economy jobs like software, research, consulting, media, and technology.
The quaternary sector is focused on knowledge-based services and depends on information technology infrastructure. Countries with robust quaternary industries tend to have more advanced economies.
Usage in Economics
In economics, the sectors describe broad economic activities:
- Primary sector – agriculture, forestry, fishing, and extraction of raw materials.
- Secondary sector – manufacturing industries that make finished products.
- Tertiary sector – service industry including retail, transportation, financial services, hospitality and tourism, education, healthcare.
- Quaternary sector – information-based services like technology, research, consulting, media, and communications.
The quaternary sector has grown as economies have shifted more towards jobs in technology, knowledge, and information services.
Conclusion
So in summary, quaternary is universally the term that comes after tertiary across disciplines. It represents the fourth stage in order and sequence after primary, secondary, and tertiary.
As seen in geology, education, industry, and economics – quaternary refers to the most recent, advanced, and complex stage of development coming after the three previous steps. Understanding this terminology sequence can provide helpful context across many fields.
