ðə sˈɪstəm ɪz əbzˈɜːvəbəl æt tˈaɪm ɪf ænd ˈoʊnli ɪf ðɛɹ ɛɡzˈɪsts ɐ fˈaɪnaɪt sˈʌtʃ ðætðə mˈeɪtɹɪks ˈɔːlsoʊ kˈɔːld ðɪ əbzˌɜːvəbˈɪlᵻɾi ɡɹˈæmiən ɪz ɡˈɪvən bˈaɪ
The system  is observable at time  if and only if there exists a finite  such that the  matrix also called the Observability Gramian is given by