Replace words from one column in another column in a text

I am trying to replace words from one column in another column in a text:

Text:

  

While these delays were noted, active nuclear power plants have been building individual warehouses within their facilities to store the dangerous spent fuel from their reactors.

Column text:

  

verify, they verified

     

this, these

     

delay, delays

     

the, the

     

central, central

     

nuclear, nuclear

     

have, have

     

go, gone

     

build, build

     

warehouse, warehouses

     

individual, individual

     

its, its

     

installation, installations

     

spend, spent

     

reactor, reactors

     

meter, m

     

second, s

     

page, p

     

actor, actors

Script:

import csv

with open('teste_es.csv', 'r') as f, open('lemas-lexemas.csv', 'r') as c:
    csv_texto = csv.reader(f)
    csv_lemas = csv.reader(c, delimiter = ',')

    for p in csv_texto:
        texto = ''.join(p)
        texto = texto.lower()

        for tokens in csv_lemas:
            lemas = tokens[0]
            lexemes = tokens[1]

            nuevo_texto = texto.replace(lexemes, lemas) 

            texto = nuevo_texto

        print(nuevo_texto)

Result:

  

Within a second second, the rear-end cluster or the active nuclear power station will have to be converted to a single centimeter within seconds, depending on the page to save the second page, or it will be possible to drill down from the second reactor.

The problem is that my program replaces letters within words:

while it became metro in the second because the first letter "m" is replaced by "metro". I do not know how to make each word be replaced. Yes I can use split (), but I have many lines in my text and I can not lose them (if I do a split () and then a join (), I lose my split lines)