Count number of sentences in a memo

If a sentence is defined as "ending with a dot", then you'll have to count the dots, or do something like
memo1.lines.linebreak := '.';
count := memo1.lines.count;

made a more generic demo below. can be customized according to what a sentence is and what a word is (see the constant set of chars defined)

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Contnrs;

const WhiteSpaces=[' ',#9{tab},#13,#10];

      punctuation=['.',',','!','?'];

      other=['(',')','+','=','<','>','/','\','{','}','[',']'];
      // I put anything that is not whitspace but is can be a word delimiter here.

      AlphaNumeric=['a'..'z','A'..'Z','0'..'9'];

type EEmptySentenceException=class(Exception)
     end;

     TSentence=class
     private
       FWords:TStringList;
       function GetCount: integer;
       function GetWord(index: integer): string;
       procedure SetWord(index: integer; const Value: string);
     public
       constructor Create; overload;
       constructor Create(s:string); overload;
       destructor Destroy; override;

       class function isWordDelimiter(c:char):boolean;

       property Count:integer read GetCount;
       property Words[index:integer]:string read GetWord write SetWord;
     end;

     TSentences=class
     private
       FSentences:TObjectList;
       function GetCount: integer;
       function GetSentence(index: integer): TSentence;
     public
       constructor Create; overload;
       constructor Create(s:string); overload;
       destructor Destroy; override;

       class function isSentenceDelimiter(c:char):boolean;

       property Count:integer read GetCount;
       property Sentences[index:integer]:TSentence read GetSentence;
     end;

{ TSentence }

constructor TSentence.Create(s: string);
var i,j:integer; w:string;
begin
  Create;
  i:=1;
  while i<=length(s) do
  begin
    setlength(w,length(s));// maximum possible
    j:=1;
    while (i<=length(s)) and (not isWordDelimiter(s[i])) do
    begin
      w[j]:=s[i];
      inc(i);
      inc(j);
    end;
    dec(j);
    if j>0 then
    begin
      setlength(w,j);
      FWords.Add(w);
    end;
    while (i<=length(s)) and (isWordDelimiter(s[i])) do
      inc(i);
  end;
  if Count=0 then
    raise EEmptySentenceException.Create('The sentence is empty: contains no words.');
end;

constructor TSentence.Create;
begin
  FWords:=TStringList.Create;
end;

destructor TSentence.Destroy;
begin
  FWords.Free;
  inherited;
end;

function TSentence.GetCount: integer;
begin
  result:=FWords.Count;
end;

function TSentence.GetWord(index: integer): string;
begin
  result:=FWords[index];
end;

class function TSentence.isWordDelimiter(c: char): boolean;
begin
  result:=(c in whitespaces) or (c in punctuation) or (c in other);
  // another definition of a word might be: any set oc alphanumerical characters
  // so it all depends on the definition.
end;

procedure TSentence.SetWord(index: integer; const Value: string);
begin
  FWords[index]:=value;
end;

{ TSentences }

constructor TSentences.Create(s: string);
var i,j:integer; t:string;
begin
  Create;
  i:=1;
  while i<=length(s) do
  begin
    setlength(t,length(s));
    j:=1;
    while (i<=length(s)) and (not isSentenceDelimiter(s[i])) do
    begin
      t[j]:=s[i];
      inc(i);
      inc(j);
    end;
    dec(j);
    if j>0 then
    begin
      setlength(t,j);
      try
        FSentences.Add(TSentence.Create(t))
      except
        on e:EEmptySentenceException do ;// nothing
        on e:Exception do
          raise e;// whatever
      end;
    end;
    while (i<=length(s)) and (isSentenceDelimiter(s[i])) do
      inc(i);
  end;
end;

constructor TSentences.Create;
begin
  FSentences:=TObjectList.Create(true);
end;

destructor TSentences.Destroy;
begin
  FSentences.Free;
  inherited;
end;

function TSentences.GetCount: integer;
begin
  result:=FSentences.Count;
end;

function TSentences.GetSentence(index: integer): TSentence;
begin
  result:=TSentence(FSentences[index]);
end;

class function TSentences.isSentenceDelimiter(c: char): boolean;
begin
  result:=c in punctuation;
end;

procedure TForm1.FormCreate(Sender: TObject);
var s:tsentences;
begin
  memo1.lines.clear;
  memo1.lines.add('word word s. next. making 3 on a line.');
  memo1.lines.add('now splitting');
  memo1.lines.add('one sentence on 2 lines. adding some more.');
  memo1.lines.add('now we have exactly 6 sentences on 4 lines.');
  s:=TSentences.create(memo1.lines.text);

  showmessage(inttostr(s.count));
  s.free;
end;

end.