What does pH stand for?

by: Charlene Rennick

Have you ever wondered why the “p” in “pH” is a lower-case letter while the “H” is capitalized?  What does it mean?

The “p” stands for potential and the “H” stands for Hydrogen.  Okay, so that makes it as clear as mud.  What is potential Hydrogen?   A scientific explanation would state that pH refers to the plant’s ability to attract hydrogen ions.  A less scientific explanation says pH is the acid/alkaline balance. 

Translated into a language those of us without the Ph D can understand, pH level refers to the amount of acid and alkaline contained inside of both the water and the growing medium or soil.  If the environment is too acidic, that means the plant will not attract enough hydrogen, while an environment that is too alkaline will attract too much hydrogen.  An environment that continually fluctuates from one extreme on the pH scale to the other is unhealthy for the plant.

Hydrogen is one of four elements any living plant needs to survive.  Without hydrogen, the plant would wilt and not be able to take in nutrients.  Because the plant contains hydrogen, it continues to absorb hydrogen through the water via a process called osmosis.  This hydrogen-osmosis cycle is what keeps the nutrients traveling from the water into the plant.  Once a plant has died due to lack of water, there is no amount of water that can be added to it that will cause the plant to be revived.

The level of pH is measured on a scale of 0 to 14 with 0 representing the highest concentration of acid and 14 representative of the most alkaline.   Seven is the magic figure for pH because it means that there is a balance of acid and alkaline in the solution and is often referred to as pH neutral.  It is usually sufficient to say that a pH neutral environment is perfect for most plants, but some vegetation requires water or a growing medium that is more acidic than alkaline in order to flourish or have the right colour of blossoms, while other plants prefer the opposite.  Testing strips for pH can be purchased to determine exactly what the acid/alkaline balance is in your water, growing medium or soil.  This makes it easy to adjust the level for home gardeners or for mixing nutrients for your own hydroponic garden.


  1. If your doing a science project this site is perfect.

  2. This really clarifies alot, without involving the principles of physics. Thanks

  3. Heaps of help with my science assignment. Explains better then my teacher.


  4. “The level of pH is measured on a scale of 0 to 14 with 0 representing the highest concentration of acid and 14 representative of the most alkaline.”

    That is not true! pH values can actually range from lower than 0 to higher than 14. Take for instance 2 M HCl: the pH would be -log2 = -0.30. The 0 and 14 values are just given as endpoints because they represent the pH of 1 M H+ and 1 M OH-, respectively, which provides a good reference point.

  5. “Hydrogen is one of four elements any living plant needs to survive.”

    This is not true either. There are many more elements that plants need to live, just like humans. Maybe they only need four elements in large concentrations, but other nutrients and minerals are needed as cofactors and coenzymes that are essential for enzymatic activity and plant functions. How about sodium and potassium? If you don’t have those, you can’t have action potentials!

  6. im doing a science fair project and it helped alot thanks. But i still dnt quite get why the p is in lowercase and the H is in captial can you clarify that a bit more?

  7. When I asked my chemistry teacher (who was head of the science faculty) what pH stood for he scratched his head thoughtfully for a few moments, then admitted that he didn’t know, and had never considered it before.

    Its funny how many things we just accept without thinking about it.

    If a man says a foolish thing – it is a foolish thing.
    If a million men say a foolish thing – it is still a foolish thing…..

  8. Herby Romulus says:

    this website is very helpful, thanx

  9. Hey thanks for this site!!!! It really helped me!

  10. What science project are you doing?

  11. this sight is awesome!!!!

    thank you for everything. this website rocks and is perfect for my upcoming science fair project.

    some of the commenters have given us their knowledge about pH also. thanks to bothe the site and commenters!!!

  12. this is so cool.the info is straight forward and to the point. i appreciated this info alot thanks!!!!!

  13. Helped me to understand a lot, thanx. That Shane person is v. nerdy! For Amy, H is a capital because on the periodic table it’s like that. For lowercase p, it’s probably coz potential is not a proper noun so it wouldn’t usually have a capital anyway.

  14. Michelle Skywalker says:

    WOW this really helped!!!

    p.s Ya my acualy last name is Skywalker im not joking lol
    serusly im not

  15. wow this is cool thanx

  16. this helps sooo much when ur in 8th grade trying to do a science fair background reserch (reserch paper) the night before it is due and u alreaddy had a sport that night and you also have to do a biboliography.. lets just say it saved me a tonn of time…
    thanks a million!!! :D

  17. pH stands for Power of hydrogen not potential Hydrogen just pointing that out there

  18. Ya same as u tiffany, im doing my sci. project report rite now!!!!! thanks for this website, i was sooooooo confused about this pH thing!!! :)

  19. This helped me soooooooooooooooooo much with my science experiment!!!!!!!!!!!!!!!!

  20. This helped a lot with my science fair project.

  21. Thanks a ton! Helped me on my science project :-)

  22. jeremy woods says:

    thankx this website helps me so much. you gus know a lot about potential hydrogen.

  23. why is p lower case a H upper case?
    thats what i need ta know

  24. The abbreviation pH stands for potential hydrogen. This abbreviation is always spelled with a small ā€œpā€ and a capital ā€œH.ā€
    In scientific terms, what pH would stand for is ability of molecules to attract hydrogen ions. An acidic molecule would have a low ability to attract hydrogen ions, while an alkaline molecule would have a high ability to attract hydrogen ions. The pH of a solution is measured on a scale from zero to 14. On the pH scale, zero would stand for the highest possible acidity reading, 7 is neutral, and 14 is the highest alkalinity reading.
    What pH stands for in the human body is a more specific study of the acid and alkaline environment within your bodily fluids. The human body strives to maintain a slightly alkaline pH at all times. Various organs inside your body help maintain this pH, including your kidneys and your lungs. Certain foods, once digested in your body, are known to leave behind an acidic pH, which your body must correct to maintain the proper pH balance. It is believed that, through a proper diet, buffering agents, and pH testing, you can help your body sustain a healthy pH balance.

  25. Dibyendu Mukherjee says:

    Well explained Ayaaz…!!!

    Further to this, the Scientists of Oncology (study of Cells) or in other words those who are Researching on Cancer are reaching a conclusion that every living body carries Cancerous cells but if the environment inside the body is more Acidic in nature, chances of multiplication of Cancer (malignant) cells are higher.

    So it is necessary to keep our body’s pH balanced by consuming less of food that create more Acidic environment within the body. Researchers suggest an Alkalinic environment is good for a Good & Healthy body to keep the growth of Cancerous/Malignant cells at bay.

    That can be controlled well with Fruits like Bananas, Dates, Almonds etc. plus vegetables contaiting Lycopene (tomatoes).

    By avoiding Lactic acid (milk), Alchohol, red-meat etc. we can reduce the Acidic environment in our bodies.

    Potency or Power of Hydrogen can be mentioned as ‘ph’ or ‘PH’ since the chemical symbol of hydrogen is capital ‘H’ so we can’t make it a lower case ‘h’…

    In this case we could have written ‘PH’ but that would sound as a short form of ‘Phase’ so to avoid any confusions we keep the chemical name of Hydrogen intact/as it is by mentioning a capital ‘H’
    and potency/power is mentioned as a lower case ‘p’ so that it can be ‘distinguished’ well.

    …This is what is my view and it sounds logical too, since we wouldn’t find any Explanations of this anywhere (at least i didn’t) in our Chemistry books…

  26. FARJANA AFRIN says:

    why the range or limit of pH 14?

  27. This helped alot with our project.We got to present our project at a science fair at Kapiolani Community center. It was so fun!

  28. The ‘H’ in ‘pH’ is capitalized for the simple reason that it (Hydrogen) is a PROPER NOUN

  29. srinivas says:

    This really clarifies alot, without involving the confused principles. Thanks

  30. The measure of acidity of a substance is known as pH. Pure water, which has pH of 7, is neutral. Substances with a pH less than 7 are considered acidic and substances with a pH of greater than 7 are considered basic.
    The normal pH of blood running through arteries (large elastic-walled blood vessels that carry blood from the heart to other parts of the body) is 7.4; the pH of blood in the veins (vessels that transports blood to the heart) is about 7.35. Normal urine pH averages about 6.0. Saliva has a pH between 6.0 and 7.

  31. flowerchild says:

    Don’t hate on nerds, they will be the most successful in life. Just think, if it weren’t for nerds, people would actually have to try in school instead of cheating and being lazy. Imagine what our world would be like if everyone worked to their full potential. Thank you for your website and thanks to everyone who posted a comment. Im working on an AP assignment where we were asked to do some research on pH. This website didn’t answer all of my questions, but it did help me with part of it and helped me to think of new questions to search for.


  1. [...] scientific explanation would state that pH refers to an organisms ability to attract hydrogen ions.

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