Reducing number of levels of indentation for plural stemming code in python

Question

My code works fine and it exactly does what it is suppose to do. However, it has too many levels of indentation. I wonder if anyone here has anyway to reduce number of levels of indentation.

Below is my code. The section I am mostly concerned about is the plural section.

#Returns stemmed sentence

def pos(sentence):

    if sentence == " ":
        return " "

    final_sentence=''
    word_list=sentence.split(" ")   
    vowels=['a','e','i','o','u','y']
    vowelFound=False
    final_word=''

    for word in word_list:

        #Remove ownerships
        if '\'s' in word:
            final_word=word.replace('\'s',"")
        elif 's\'' in word:
            final_word=word.replace('s\'',"")
        else:
            final_word=word

        #Remove Plurals
        if final_word.endswith('s'):
            if word[-2] in vowels:
                for c in word:
                    if c in vowels:
                        vowelFound=True
                        print(vowelFound)
                        break
                if vowelFound:
                    if not word.endswith('us') or word.endswith('ss'):
                        if word.endswith('sses'):
                            final_word=word.replace("sses","ss")
                        elif word.endswith('ies'):
                            final_word=word.replace('ies','i')
                            if len(final_word)<=2:
                                final_word=word
                        elif word[-2] not in vowels:
                            final_word=word.replace('s','')
                else:
                    final_word=word
            else:
                final_word=word

        #Remove past tense
        elif word.endswith('ied'):
            final_word=word.replace("ied","i")
            if len(final_word)<=2:
                final_word=word.replace("d","")
        elif word.endswith('ed'):
            final_word=word.replace("ed","")

        #Remove adverbs
        if word.endswith('ing'):
            final_word=word.replace("ing","")
            if len(final_word)<3:
                final_word=word

        if final_word.endswith('ly'):
            final_word=final_word.replace("ly","")

        #Remove adjectives
        if final_word.endswith('er'):
            final_word=final_word.replace("er","")
        final_sentence+=final_word+" " 
  
    return final_sentence